proving using calculus without trig identity

kebabs

Please I really need help with this hw question

Prove without trig identity that f`(x)=0 for

F(x)=Asin^2(Bx+C)+Acos^2(Bx+C)

SteveL27

You're not supposed to use the obvious identity that simplifies this? I suppose you could just use the derivatives of sin and cos along with the chain rule to directly compute the derivative. But eventually you'll need to simplify using some trig identity.

kebabs

I can't use trig identy to solve it

kebabs

I mean I'm not allowed to

SammyS

What is F'(x) if [itex]F(x)=A\sin^2(Bx+C)+A\cos^2(Bx+C)\,?[/itex]

eumyang

Are you sure? I was able to get F'(x) = 0 by using the chain rule, and yet I didn't use any trig identity.

kebabs

could you please send me your working for this question??

Ansatz7

It's really simple - just use chain rule to take the d/dx of the whole expression. No trig or any other kinds of tricks necessary. Are you familiar with the use of chain rule?

Mark44

This is not permitted at Physics Forums - don't even ask.