What is the derivative of (cos^2(x)sin^2(x))(cos2(x)sin2(x))?

1 Answer
Nov 29, 2016

We could calculate the derivative using the product rule

(d(f*g))/(dx) = (df)/(dx)* g+f*(dg)/(dx)d(fg)dx=dfdxg+fdgdx

However we can also note that:

sin(2x)=2sinxcosxsin(2x)=2sinxcosx

so:

f(x) = cos^2(x)sin^2(x) = ((sin2x)/2)^2=1/4sin^2(2x)f(x)=cos2(x)sin2(x)=(sin2x2)2=14sin2(2x)

Using the chain rule:

(d(1/4sin^2(2x)))/dx= 1/4*2sin(2x)cos(x)* 2 = 2sinx * cos x * cos x= 2sinxcos^2xd(14sin2(2x))dx=142sin(2x)cos(x)2=2sinxcosxcosx=2sinxcos2x