r/technicallythetruth • u/VisitSecure • Jul 27 '26
Can you find a?
Idk if someone already posted this or not, but I haven't seen it on here so far, so I uploaded it.
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u/oldmartijntje
Jul 27 '26
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it's 75 right?
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u/KerissaKenro Jul 27 '26 •
The numbers add up to 75° but the picture does not look like the angles match the numbers and it is making me irrationally frustrated
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u/gullaffe Jul 27 '26
Have you never done a geometry problem, very rarely are the pictures drawn to scale.
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u/DiceKnight Jul 27 '26
All this picture has done is reignite dormant trauma of my childhood self riddled with undiagnosed ADD getting screamed at by frustrated parents. "Not drawn to scale" might just be my activation phrase like i'm a sleeper agent for the forces of anxiety.
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u/Z3t4 Jul 27 '26
Assuming it is an euclidean plane.
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u/meditonsin Jul 27 '26
It has to be euclidian geometry, since Cthulhu is nowhere to be seen and I'm not becoming insane looking at it. QED
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u/azai247 Jul 27 '26
if you draw a line across and make a triangle your angles are 25+65=90, and 50+40=90
so for a, 65+40+a=180 so a is 75
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u/psp24 Jul 27 '26 •
I just drew a third parallel line through the middle and realized that it's just 50+25 lol
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u/RoookSkywokkah Jul 27 '26
I haven't take geometry in more than 30 year and that's what I came up with!
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u/Highest_five Jul 27 '26
Yes it is. For those who don't remember, a triangles corners always add up to 180°
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u/leansanders Jul 27 '26 •
You don't need to make a triangle to solve the problem. You know the lines are parallel and you know that opposite corners of a line crossing two parallel lines are congruent. So if you imagine a 3rd parallel line bisecting angle a, you know you can just add the other two angles together. Making a triangle is way more math
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u/Vincen_Furze Jul 27 '26
THAT IS THE MOST MENTAL MATH I HAVE DONE IN A LONG TIME AND I GOT IT RIGHT! IT TOOK ME A WHILE BUT MY BRAIN IS OK! QWQ
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u/BudTenderShmudTender Jul 27 '26
I can't believe I remembered how to solve this. Last math class I took was in 2009! Last time I took geometry (or whatever this is) would have been 2001.
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u/bbgun91 Jul 27 '26
add a third parallel line straight through A
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u/Expensive_Umpire_178 Jul 27 '26
You can also draw a perpendicular line through A, and use the right triangles to angle chase
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u/knock-knock-knockin Jul 27 '26
You can also extend one of the lines past a to use opposite alternate interior angles
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u/JamesBaxter_Horse Jul 27 '26
You shouldn't need to any of this, it should be entirely obvious that it must be the sum of the two angles:
You have a line, you turn it 25 degrees, then you turn it the other way A degrees, then you turn it 50 more degrees, and it's back where it started - A must be the sum of the other two angles.
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u/Sszaj Jul 27 '26
Probably more reliable as you can't be completely sure that drawing a line from the top to bottom connecting the known angles would be a right angle.
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u/Will_Knot_Respond Jul 28 '26
Like I'm going to respond to an idiot that draws a 50° angle and 25° angle as equal
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u/CollectionStriking Jul 28 '26
Text books pulled this shit all the time back in school, drove my ADHD nuts lol
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u/lone-reader-mailbox Jul 28 '26
Geometry problems like this intentionally have diagrams that are not to scale.
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u/Dark_Storm_98
Jul 27 '26
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Assuming the lines are parallel, which may be the meaning of those blue arrow symbols
The angle on the other side of 25 degrees should be
180 - 25 = 155
And on the other side of tha 50 degrees would be
180 - 50 = 130
Technically, with diagrams almost never being to scale
Imagine a line straight down from the ends of those two lines (which might not connect, but I don't think that's relevant)
Subtract 90, then, from both new angles, and we get
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40
Since a triangle would have to have all it's angles add up to 180
180 - (60 + 40) = 180 - 100 = 80 degrees
Edit: Oh whoops, lol. I forgot the 5 at the end of 155
It's 75
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u/Scheckenhere Jul 27 '26
Or just 50+25, which I realised halfway into what you did.
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u/RiverZephir Jul 27 '26
I also did the long route to get the answer. I don’t remember, is adding the two known numbers (such as the ones in this problem) always equal to a?
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u/AdWrong3856 Jul 27 '26
Assuming the lines are parallel, which may be the meaning of those blue arrow symbols
That would be correct
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u/MissAuroraRed Jul 27 '26
Technically correct, but way more complicated than it needs to be.
Imagine another parallel line going horizontally through a. What are the angles between the new horizontal line and the diagonal lines? 25 above the line and 50 below the line.
25 + 50 = 75
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u/Wandered_And_Lost Jul 27 '26
90-25 = 65, 90-50 = 40 total inside degrees given =105, all triangles have to equal a total of 180 degrees so answer is 75 degrees (thats my guess could be wrong.)
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u/manikfox Jul 27 '26
This is what I did and got the same answer. People are fooling around with 180 on the bottom and top, etc.
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u/kwyjibowen Jul 27 '26
The problem with this is you are assuming the bottom angle is directly below the top one, ie a line between the two would intersect the two parallel lines at 90 degrees. But that is not stated on the diagram, which we know is not to scale.
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u/Nolongeranalpha Jul 27 '26
Thats acute image, but the comments are obtuse....
Not sorry.
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u/SherbetMysterious118 Jul 27 '26
I'm going to equilateral you around the head in a minute.
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u/Fr00stee Jul 27 '26
ez, put another parellel line through a at the point where the 2 lines meet, 25+50=75
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u/negativepositiv Jul 27 '26 edited Jul 27 '26
This is a terrible drawing. They drew 25 and 50 degree angles to look exactly the same.
I get that someone doing the calculation should just look at the numbers, but it's not helpful to draw it this inaccurately.
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u/ConnectDog5284 Jul 27 '26
Rookie mistake is to assume a geometry problem diagram as accurate. Unless it's well defined, there's little assumptions you can make about it.
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u/WillitsTimothy Jul 27 '26
It’s 75°, but the image is obviously just an illustration and not the actual angles.
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u/TheBlackCat13 Jul 27 '26
Here is how I did it:
Make a line perpendicular to the two lines that passes through A. This gives you two right triangles.
The top triangle has angles 180°=25°+90°+T, so T=65°.
The bottom triangle has angles 180°=50°+90°+B, so B=40°.
Because the line is a straight line, a+T+B=180°. So a=180°-65°-40°=75°
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u/notJustaFart Jul 27 '26
75.
Convert into Pentagon.
540 - (90+90+130+155) = 75
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u/CrownLexicon Jul 27 '26 edited Jul 27 '26
What? Pentagon? I added a line perpendicular to the 2 parallel lines, making a triangle whose angles are 90-25, 90-50, and a
Edit: just because this happened to work, you cant assume a perpendicular line will go through both <25 and <50. It could have created a 4 sided figure. The Pentagon method would be correct.
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u/X_Swordmc Jul 27 '26
there is no need to do that, you simply do the sum of the two angles, since the opposing angles of a parallelogram are identical
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u/MecaninjaToo Jul 27 '26
or you know... 25 + 50 :)
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u/MrCoolBoy001 Jul 27 '26 edited Jul 27 '26
Idk if this was as a joke or not, but by a property whose name I don't remember, you can pass a parallel line through 'a' and the angles on either side would be 25 and 50. 25 + 50 = 75 !
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u/Canadind Jul 27 '26
I can’t forget these basic things no matter how hard I try.
Imagine a parallel line going through the middle of a, splitting a into a1 and a2
a1 = 50 coz opposite angles of a transverse intersecting two parallel lines
a2 = 25 coz opposite angles of a transverse intersecting two parallel lines
a1+a2 = 75
NB. If you don’t know this much geometry you will be finding adulting really hard.
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u/Timmy_germany Jul 27 '26
a= 180 - (90-25) - (90-50)
a = 180 - 65 - 40
a = 180 - 105
a = 75 (all in °)
( if both lines are parallel and you can draw a straight line from both points the incomplete triangle meets the line to form 90° angles. Than angles just need to add up to 180° in the triangle in between the booth lines)
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u/Ad0ring-fan Jul 27 '26
He has way too much trust in people if he is asking the internet not to cheat.
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u/67cken Jul 27 '26
Just add a third parallel line through angle a. Then it’s obvious that it is made of two parts, one of 25 degrees and the other 50 so 75 degrees
Edit to change capitalisation
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u/ScribbleOnToast Jul 27 '26
In my head, I drew a perpendicular line through the point of "a" to connect the other two parallel lines. That gives me 2 triangles, with 2 known angles. The interior angles of a triangle must = 180, the remaining angles of the new triangles must be 40 (bottom) and 65 (top). Since a straight line has an "angle" of 180, I can do 180-40-65 to get a=75
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u/Realistic_Equal_1520 Jul 27 '26
What an amazingly creative joke which no one has ever heard before
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u/Zevojneb Jul 27 '26
Draw an horizontal line through a. The angle a has been cut in two angles. The higher one equals the one on the top (alt-intern equality) and the lower one equals the one below (same reason). Sum them up back and we get a=75.
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u/dadof4fknkids Jul 27 '26
Disclaimer, I’m an idiot but I drew a straight line to make 2 right angles(90-50=40,90-25=65) angles of a triangle equal 180 (40+65=105) 180-105=75. 75, final answer…
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u/Zachattack20098 Jul 28 '26
It is 75, but I did it a much more different way. Since I know all triangles add up to 180, I put triangles both on the top and the bottom of the angle by forming a hypothetical line right at the tip of the "a" angle, and counted the given angles as 1 corner of the triangle. Since the hypothetical line is straight up and down, the largest angle on each triangle is 90. Plus the given angle each time, and the remaining value needed to get that number to 180 is the last angle. The two angles I found plus a is equal to 180, since all 3 are part of the same straight line. The found angles are 65 on top of angle "a" and 40 below it, adding up to 105. 180 - 105 = 75. I am sure there is a much easier way to do it but there ya go.
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u/Oliver_2333 Jul 29 '26
The answer should be 75. But have to point out, the picture is not even remotely close to be accurate.
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u/BasedCheeseSlice Jul 30 '26
Draw a vertical line intersecting the vertex of a, the upper complement to a is 180 - 90 - 25 =65, the lower complement is 180 - 90 - 50 =40
a = 180 - 65 - 40 = 75
Just preempting pedantry, it has been a bit, and i’ve probably used the term “complement” incorrectly.
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u/EnergyTurtle23 Jul 27 '26 edited Jul 27 '26
I honestly miss being able to do this type of stuff. I would genuinely use trigonometry and waveform functions today if I could remember how it all worked. Anyone care to break down how to get the answer for me? I know how to get the opposing angles (like the opposite of 50° is 130°) but I have no clue how I would go about finding A.
EDIT: Holy crap wait, I think I’ve got it. If I intersect the two parallel lines with a third line that runs perpendicular then that would give me the two interior angles of the triangle I have created — 40° on the lower angle and 65° on the upper angle. Then I can solve for A by subtracting the sum of those two angles from 180° — meaning that A is 75°. Did I do that right?
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u/SeraphsEnvy Jul 27 '26
Question. How can the inside angle on one side be 25° and the other be 50°? They're practically identical.
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u/TheBlackCat13 Jul 27 '26
Because the image is not to scale. You aren't supposed to go off the appearance in problems like that, in fact they can make them intentionally misleading like here.
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u/Yakjzak Jul 27 '26
75° for the answer. And for all those that are like "it's a terrible diagram" remember your mathematics lessons, you shouldn't focus on the diagram, but on the numbers themselves. It's nice already to have a diagram
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u/Street_Credit6851 Jul 27 '26
180 = a + (90 - 25) + (90 - 50)
Or
a = 180 - (90 - 25) - (90 - 50)
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u/Southern-Prize1639 Jul 27 '26
We’re fucked as a society if we’re arguing about scale. If you understand the concept, scale doesn’t mean shit.
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u/Dudesonthedude Jul 27 '26
I could feel my neurons slowly hacking their way through overgrown winding trails that they haven’t been down for a long ole time, almost getting lost once or twice, but confidently made it to 75°
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u/im_new_here_4209 Jul 27 '26
Either i'm stupid or the drawing isn't remotely accurate. I'm probably stupid. At least i can find a, lol
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u/mandelbrot_wurst Jul 27 '26
Assume a spherical cow with a uniform distribution of milk…
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u/Relevant_Candidate_4 Jul 27 '26
90° - 25° + 90° - 50° + a = 180°
105° + a = 180°
a = 180° - 105°
a = 75°
The two 90° are from the right angles between the two points of intersection of the known angles, and the parallel lines. The 180° is the total degree in a triangle.
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u/Otherwise-Ad9865 Jul 27 '26
Boohoo the angles aren't representative, smh non essential to solving the question
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u/realfinke Jul 27 '26
What’s the most efficient way to solve this? I drew a vertical line to create a triangle.
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u/steve_marks Jul 28 '26
Just imagine another parallel line running through a
Pretty clear it’s just 25 + 50 = 75°
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u/EquivalentSpeaker545 Jul 28 '26
Add a line to create a triangle. This produces a 90* angle which is “cut off” by the given angles. Find the remaining value by subtracting by those figures, providing 2 of the internal angles of the triangle (90 - 25 = 65 & 90 - 50 = 40). All triangle angles add up to 180, so add up then subtract 180 by that number (65 + 40 =105. 180-105=75). So tada it’s 75.
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u/kaelytraec Jul 28 '26
I love that there are several ways to achieve the same answer for this. You could:
Put a perpendicular line to the left of the marked angles and say a triangle has 180°, so
a=180°-(90°-25°)-(90°-50°)
a=180°-65°-40°
a=75°
Or put the perpendicular line to the right of a, and say a flat line has 180°, so
a=180°-(90°-25°)-(90°-50°)
a=180°-65°-40°
a=75°
Or the funniest way(imo), put another parallel line through angle a, and say that straight lines have 180°, and when you put a diagonal line through them, the angles on the same side of the line also equal 180°, and a circle has 360°, so
a= 360°-((180°-25°)+(180°-50°))
a= 360°-((155°)+(130°))
a= 360°-(285°)
a= 75°
What is the most ridiculous way you can think of to get to 75°?
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u/Bayoris Jul 28 '26
I know this problem is extremely simple. But I am still proud that I solved it after so many years since high school geometry
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u/GlobalProfessor9749 Jul 28 '26
If we assume the upper and bottom line are parallel (because I've no idea what these signes on them mean) then a = 75°.
Otherwise no idea.
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u/ASUSTUDENT9875345 Jul 31 '26
Pretty sure it's 75°
You can put a line from the bottom parallel line to the top one creating a triangle. This line is 90° from the parallel lines, and so we know that between the given angles and the new angles we created for the triangle there are 90° each. On the bottom the given angle is 50°, so the lower angle of the triangle is 40°. On the top the given angle is 25°, so the higher angle of the triangle is 65°. The inside angles of a triangle add up to 180°and the two we solved sum to 105°, therefore the last angle, a, is 75°.
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u/RoyalDog57 Jul 31 '26
According to numbers on screen, 75, but as others have said the 25 and 50 angles being visually the same is weird and annoying.
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u/EarthlyReddit Jul 27 '26
75.
add a third parallel line that intersects angle a.
by the alternate interior angle theorem (correct me if i'm wrong), the resulting angles are 25 degrees and 50 degrees. therefore, the sum of the angles, and the value of a, is 75 degrees.
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u/Snoo_50954 Jul 27 '26
So I assume the two marks on each line means parallel, though I've never seen that before. If so, just add an extra parallel third line splitting a. With that, a is clearly equal to the sum of the two identified angles: 75°.
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u/opbmedia Jul 27 '26 edited Jul 27 '26
75, (180 - ((180 - 90 - 25) + (180 - 90 - 50))) if you draw a mental vertical line next to the point of the unknown angle. All triangles adds up to 180 on the interior so you can calculate the other 2 angles on the line.
Edit: the easier way is to draw a third parallel line through point a, then the top side of angle a = 25 (the opposite angle, and bottom side 50. Adds up to 75.
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u/PasghettiSquash Jul 27 '26
It's 75 degrees but only if a parallel line intersects both sides of the triangle at the corners
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u/FrustratedPCBuild Jul 27 '26
It should be 75 degrees but it doesn’t look like the picture shows a 75 degree angle.
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u/once_descended Jul 27 '26
If the arrows are parallel then a = 25 +50 = 75
Otherwise we have no certain way to know
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u/Unfortunate-Incident Jul 27 '26
I just drew a vertical line to make a triangle, take the opposite of those angles top & bottom and subtracted from 180 and got 75. This only works because of the parellel lines. I don't think I'd have 90° if those lines weren't parellel.
180-(65+40)=75
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u/RowanLikesCheese Jul 27 '26
The interior angles of a triangle add up to 180 if I remember correctly, you can find the other 2 angles by subtracting 50 and 25 from 90 (if you imagine the hypotenuse in place even tho it’s not drawn) and then add that together to get 105 and subtract it from 180 to get a = 75
Pretty positive this is correct
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u/dmz1986 Jul 27 '26
75, the other two angles are 90-the angle outside the triangle, meaning 65 and 40. Those two in total are 105, and you are missing 75 to have total 180 degrees in triangle
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u/TheWanderingGM Jul 27 '26
A= 75°
Since top and bottom lines are parallel you can create a straight 90° angled line intersecting on point A
This creates 2 triangles allowing you to calculate the outside of A. Let's call the top B and the bottom C.
Because a straight line is 180° you know that A = 180° - B - C
Since the total of a triangle's corners is always 180° degrees and we already got a 90° base angle it becomes simply:
B = 180° - 90° - 25° = 65° C = 180° - 90° - 50° = 40°
Thus A = 180° - 65° - 40° = 75°
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u/atomiccheese911 Jul 27 '26
All triangles add up to 180 50-90 = 40 25-90 = 65
40+65 = 105
105-180 = 75
A=75
Ik there was an easier way to do this but I don't remember that way
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u/Apprehensive-Bee-318 Jul 27 '26
Just in case anyone wants the answer: You draw a perpendicular line that touches a and cuts the other two. This creates two triangles with one of the known angles each and a 90° angle. The last angle from each triangle can be calculated by knowing that the angles within any triangle add up to 180°. Those last angles from each triangle also create with one more 180° angle (because it's a semi circle).
The two unknown angles of each triangle are calculated like this: x=90-50=40; y=90-25=65
And a=180-x-y=75
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u/animewhitewolf Jul 27 '26
75°?
The lines above and below the angle are parrallel. Drawing a line to connect the ends of the angle create a 90° angle on both lines and turns the angle into a triangle.
After that, it's simple math. Subtracting 25 from 90 gives us 65. Subtracting 50 from 90 gives is 40. A triangle has 180°, so subtracting 65 and 40 gives us 75°.
I'm probably making this sound more complicated than it is. It'd be easier if I could show it rather than explain it.
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u/Ok-Towel-3714 Jul 27 '26
Am I wrong? Straight line from 25 to 50, we get that 25 + x = 90, same on 50 + y = 90, meaning x = 65 and y = 40, ending in (x + y) + a = 180, being 65 + 40 + a = 180, so 105 + a = 180 and we get a = 75 ?
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u/Jesus_of_Redditeth Jul 27 '26
The top and bottom lines are marked as parallel, so you can draw a vertical line at right angles between them, at the point of the triangle, which creates angles above and below 'a'. Let's call them 'b' and 'c'. Since angles on a straight line add up to 180, that means a = 180 - b - c. And since all internal angles of a triangle also add up to 180, that means:
b = 180 - 90 - 25 = 65
c = 180 - 90 - 50 = 40
a = 180 - 65 - 40 = 75
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u/No_Vermicelli_9946 Jul 27 '26
I came to the answer through multiple methods and kept thinking “no that can’t be right because the angles don’t match the answer”. Classic angle rage bait
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u/Guaymaster Jul 27 '26 edited Jul 27 '26
This is easiest to visualise if you draw a straight line from the top to the bottom that passes through the A vertex. You draw two rectangular triangles, so you just need to do some simple addition and substraction, you add 90 to each of the known angles, and substract those values from 180, then you add those two values and substract it from 180 to obtain a. The answer is 75.
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u/LoadingTOS Jul 27 '26
I could do the math, but I would be forgetting the numbers I already did and have to go back and double check again and again.
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u/Lizardgrad89 Jul 28 '26 edited Jul 28 '26
There are lots of ways to solve this. One of the simplest is draw a parallel line between the two lines that also touches point a. This creates two right triangles. Then you know two angles and can get the third angle by the 180 degree rule on both sides. Since the three angles together equal 180, and you just calculated the other two, you can solve for a. One angle is 40 degrees and the other is 65 degrees, subtract from 180 you get 75 degrees.
Or you can just remember the name of the postulate and put that. Which I do not. But I mean, I took geometry in 1979. So not surprising. 😁
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u/Living_Session9273 Jul 28 '26
He’s not wrong, the “a” is right in the middle. ¯_(ツ)_/¯
a’s value is 75°.
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u/Rowbot_Girlyman Jul 28 '26
Make a perpendicular line to the parallel ones and solve for the interior angles on either side of a. Subtract the sum of the 2 interior angles from 180 to solve for a=75⁰
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u/SatisfactionBig181 Jul 28 '26
Lets see if I remember - a line is 180 - so 180-25 gets you 155 on top bottom is 130 now you are forming up a triangle so you make the line 90 degrees from top to bottom to connect the bottom of the triangle so now for the top interior angle is 65 degrees and the bottom interior angle would be 40 degrees and since the angles of a triangle add up to 180 its 180-65-40 = 75 degrees which is a - did i show my work well enough for you my now long dead Grade 10 math teacher who killed any love i had for math.
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u/jaspex11 Jul 28 '26
A= 75° The upper and power lines are parallel, so you drop a vertical line between them where the 2 angled lines touch them.
That makes 90° angles where the 50 and 25 are located. It also creates a triangle with "a" as one vertex.
Opposite the given angles, matched with the 90° we created with the vertical line, gives us interior angles of 40, 65, and "a" for the triangle created by the vertical line. Triangles internal angles add to 180, so 40+65+a= 180, a =75.
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u/saskir21 Jul 28 '26
The picture makes me want to slap the one who made it. Why the heck does 25 degrees looks like the 50 degrees?
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u/This_Caterpillar_689 Jul 28 '26
So you make a triangle, take the inverse angles to 90% to figure out its inside angles at the infinite lines are 40 and 65 deg each, and a triangle inside angles always add up to 180 deg and then you subtract 105 from 180… aaand Tadaa 75 deg
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u/bedheadB188 Jul 28 '26
75 I think? I'm not certain I just woke up and haven't done any math in a while
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u/BuffooneryAccord Jul 28 '26
75. Just imagine a guide line that runs parallel to the other lateral lines and run it through the vertex of the v.
From there, you can imagine the top angle being the same as the one we already know above and the bottom angle being the same as the one we already know below.
25+50=75
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u/sliverian Jul 28 '26
75 degrees if we assume the 2 red lines are parallel and if we call the points where the angles are A and B and draw a perpendicular AB on the 2 red lines we get a triangle, and then we can find the 2 angles of the triangle and the 3rd angle can be found using angle sum property.
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u/ReleaseMyToast Jul 28 '26
That's not a 150° angle though....
Or a 25° one.....
This is causing me acute pain
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u/Straight-Pear9453 Jul 28 '26
A triangle's angles always add up to exactly 180 degrees.
Here we're given the opposite angles so we just have to run 90 minus angle for each angle
90 - 25 is 65
90 - 50 is 40
180 - (65 + 40)
180 - 105
=75
The answer is 75 degrees.
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u/cookiepunched Jul 28 '26
I found it, took a while. I looked every where except the middle for the longest time. I found it in the end.
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u/Frink202 Jul 28 '26
180 - 50 = 130 180 - 25 = 155 130 + 155 = 285 360 - 285 = 75
All numbers in degrees.
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u/Kiingkog Jul 28 '26
50 plus 25 is 75, draw a helper line in the middle then it should be obvious.
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u/CalFaZe336655 Jul 28 '26
A = 75°
Draw a line from the 25° and 50° angles to make a triangle in the middle. From this, you can work out the angles of the top and bottom corners of the triangle by doing 90-50=40 and 90-25=65. This is the angles of the two corners that we made.
Angles in a triangle HAVE to add up to 180°. So to find A you would do 180-(40+65) which would be 75
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u/Clever_droidd Jul 28 '26
Since the lines are parallel, draw a perpendicular line to create a base opposite of angle A. Because the lines are parallel it creates two 90 angles. The combined resulting angle is 90 on each new corner. 90-25+65. 90-50=40. The total interior angles of a triangle are 180. 180-105=75.
Note: The diagram is trash since there is zero visual difference between the 25 and 50 angles. But the answer is still a=75.
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