1 more derivative problem

1. Sep 30, 2007

BuBbLeS01

1 more derivative problem!!

1. The problem statement, all variables and given/known data
Find the derivative of...
2sinxcosx
not simplified

3. The attempt at a solution
(2cosxcosx) - (2sinxsinx)

I just want to make sure this is right

2. Sep 30, 2007

rock.freak667

yes that is correct..but you should simplify cosxcosx to $$cos^2x$$ and likewise with the sinxsinx

3. Sep 30, 2007

dynamicsolo

And, when you're done, does that result look like a trig identity you've seen before? Could you have gotten the same result by using a trig identity on 2 sin x cos x first?

4. Feb 9, 2009

MrSparky

Re: 1 more derivative problem!!

dy/dx = 2 sin x . -sin x +cos x . cos x= 2 ( cos squared - sin squared)