Posted by sean on Wednesday, May 14, 2008 at 12:12am.
Use the chain rule separately for each of the two terms. The first term can be differentiated as follows:
Let u = tan 3x and v = u^2
tan^2(3x) = v{u(x)}
d/dx [tan^2(3x)] = (dv/du)*(du/dx)
= 2u * 3 sec^2 3x
= 6 tan(3x)*sec^2(3x)
Use a similar procedure to differentiate sec^2(3x)