## anonymous one year ago cos(pi/2-x)=sin(x) True or False

1. anonymous

false, doesn't work out

2. anonymous

false

3. zzr0ck3r

$$\cos(A-B) = \cos(A)\cos(B)+\sin(A)\sin(B)$$ So in fact $$\cos(\dfrac{\pi}{2}-x)=\cos(\dfrac{\pi}{2})\cos(x)+\sin(\dfrac{\pi}{2})\sin(x)=0*\cos(x)+1*\sin(x)=\sin(x)$$

4. zzr0ck3r

@plohrb @Dwayne_Johnson This is the problem with just giving answers...

5. freckles

this is also cofunction identity compare cos(pi-x) 's ratio and sin(x)'s ratio |dw:1441062161511:dw|

6. dinamix

@Reid448 its true and we find it in (Equilateral triangle ,Triangle-based) right mr @freckles

7. freckles

equilateral triangle is a triangle with each of its angle measurements equal to 60 deg

8. dinamix

i mean should be based and equilateral

9. dinamix

the triangle

10. zzr0ck3r

thanks @freckles that is cool, I always have to look it up.