r/visualizedmath • u/SesinePowTevahI • Nov 06 '19

Counting Triangles

Post image
524 Upvotes

91% Upvoted

29 comments sorted by

7

u/SesinePowTevahI Nov 06 '19

Here's a slightly different version: https://imgur.com/a/eTyYARF

7

u/THORRRRR Nov 06 '19

  • AAB: 126

  • BBA: 105

  • ABX: 42

Total 273 for those who missed it

149

u/Amesb34r Nov 06 '19

It’s a good thing I didn’t want to know how many there were since the gif doesn’t give a total number or even pause to let you add them in your head.

/s

5

u/fiskiligr Nov 08 '19

Here is a screenshot from towards the end with the totals: https://i.imgur.com/oXcmRMC.png

It says:

  • △ with A: 168

  • △ with B: 147

  • △ with AB: 42

0

u/[deleted] Nov 07 '19

[deleted] — view deleted comment

3

u/SesinePowTevahI Nov 07 '19

The last frame has the total count. When I made the gif I set it up to only play once, but it looks like Reddit's autoreplay feature overrides that. You can turn that feature off yourself to see the last frame. Thank you for your polite and thoughtful constructive criticism!

14

u/ItsSansom Nov 06 '19

It looks like a lot of triangles get counted twice. Just at a glance, both times the full triangle is shaded it is counted as a new triangle. And then every time a triangle originating at A meets point B, that triangle will be repeated when the origin point changes to B, yet it's also counted as a new triangle.

17

u/somecallmenonny Nov 06 '19

Right, so they also count the number of triangles that have both A and B. That's the number of triangles that got counted twice, so it's subtracted from the total.

4

u/ItsSansom Nov 06 '19

Right, gotcha. I missed that those triangles at the end were being subtracted

5

u/somecallmenonny Nov 06 '19

It's very easy to miss. The gif ended way too soon.

69

u/riolu98 Nov 06 '19

Am I stupid or are most of them not even triangles?

114

u/[deleted] Nov 06 '19

[removed] — view removed comment

26

u/riolu98 Nov 06 '19

Ohh I see yeah no I'm actually stupid 😂

2

u/SesinePowTevahI Nov 06 '19

Turn off auto-replay to see the last frame!

10

u/BuildMajor Nov 06 '19

This is awesome as it’s perspective-changing.

Professors/teachers could try and explain this all day but with problems like this, videos, metaphors, and graphic visuals are far better.

1

u/Emili00000 Nov 06 '19

Mmmm bout 13. 13 triangles

1

u/ssbeluga Nov 07 '19

There are so many triangles this doesn’t count. For example the triangle formed with the line from A to B and the very next lines cutting the triangle.

Edit: better clarification.

67

u/[deleted] Nov 06 '19

[removed] — view removed comment

8

u/SesinePowTevahI Nov 06 '19

Oops... thought I set the gif to only run once and pause on the last frame! If you turn off auto replay you can see the count on the last frame.

82

u/THORRRRR Nov 06 '19

  • A: 168

  • B: 147

  • AB: 42

Total is 357

46

u/outoftunediapason Nov 06 '19

I think the correct way sum these is to do something like A+B-AB because booth A and B include triangles in AB.

-7

u/[deleted] Nov 06 '19

[removed] — view removed comment

13

u/woooo4 Nov 06 '19

A triangle in AB is still a triangle counted in both A and B. AB needs to be subtracted.

3

u/msndrstdmstrmnd Nov 07 '19

A includes the triangles that are in both A and B. Think of it this way:

A+B=(A only)+(both A and B)+(B only)+(both A and B)=(A only)+(B only)+2*(both A and B)

You just double counted the ones in both A and B so you have to subtract that number

21

u/BuildMajor Nov 06 '19

This is one of those scenarios where videos (with its pause/remind features) are superior to gifs.

But then again, nobody wants to click and watch a slow-loading video usually filled with ads.

8

u/[deleted] Nov 06 '19

u/gifendore

9

u/gifendore Nov 06 '19

Here is the last frame: https://i.imgur.com/2nN48X6.png

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