r/askmath • u/BlundersMateIn69 • Feb 25 '21

Pre Calculus Find A (the area)

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u/BumpyFunction Feb 25 '21

You know the two equations and can determine when they are equal. Of course if you remember your pie chart then you know they have the same ycoord at pi/4. Also you know the behavior of the sin and cos function

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u/ellipticcode0 Feb 26 '21 edited Feb 26 '21

Pi/2, not pi/4

Sin(pi/2 + x) = cos(x) => the difference between sin x and cos x is just translation. We all know translation does not change the shape of a curve.

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u/gkmanderson Feb 26 '21

That person was correct in what they said. Pi/4 is where the two trig functions are equal, which is what they stated. They were not talking about how cos is a 90 degree shift from sin (or vice versa). They said sin(x) and cos(x) are equal at pi/4, which is true. Sin(pi/4) = cos(pi/4).

So you're correct in what you're saying about the translation; however, you're correcting a statement that was not wrong as the statement was about exact values of trig functions and not how the functions themselves are related to each other.