Posted by Juliet on Sunday, September 18, 2011 at 2:16pm.
differentiate:
y=sin^2(x) cos^2(x)
I have this:
y'= 2cosx + 2sinx
What do i do next??

Calculus  Reiny, Sunday, September 18, 2011 at 5:01pm
Ahhh, you might recognize that
cos^2 x  sin^2 x = cos 2x
so y=sin^2(x) cos^2(x)
=  cos 2x
dy/dx = 2sin 2x or 4sinxcosx
If you don't see that identity right away, then
dy/dx = 2(sinx)cosx  2cosx(sinx)
= 4sinxcosx or 2sin(2x) 
Calculus  Anonymous, Monday, September 19, 2011 at 10:39am
Oh! Thank you so much! I completely forget about the double angle identity!!! :)
THANKS!!!