Im doing this differential and used the chain/product rule up untuil i cannot simplify any further. Its quite messy and ive spent ages looking for a way to do it. The Q was differentiate with respect to x and simplify where possible

$\displaystyle sin^3xcos3x+cos^3xsin3x$

I got down to:$\displaystyle \frac{sin^3xsin3x}{3}+3sin^2xcos3xcosx+\frac{cos^3 xcos3x}{3}-sin3xcos^2xsinx$ a bit long dont you think?