Thread: Cofunction identity

Im trying to verify the identity cos (X-pi/2)= sin x

Can someone please break down? Literally step by step. And indicate which identities r being used.

Thank you.

Cos (x-pi/2)=cos(x)cos(pi/2)+sin(x)sin(pi/2)

Simplify.

Yes, i figured as much using the sum and difference identity. Dont know what to do afterr that.

Well, cos(pi/2)=0 and sin(pi/2)=1 so you end up with sin(x)=sin(x).

Ohhhhhh....drat...didnt realize had to look at them individually, i was too bz just figuring out how to cancel each other out to get sin x alone. Thanks so much!

Click here for a proof of cos (a-b)=cos(a)cos(b)-sin(a)sin(b)