Calculus
posted by Tom .
y=cos3x(sin^3)x

What do you want to do with the equation?
Do you need to differentiate the righthandside?
Treat it as a product of cos(3x) and sin³(x) and within each, use the chain rule.
dy/dx=3sin(3x)sin³(x)+cos(3x)*3cos²(x)
and simplify.