## marigirl one year ago Can you please explain.. integrate 2 cos^2(x)

1. anonymous

probs a good idea to use trig identities

2. anonymous

$\cos(2x)=2\cos ^{2}(x)-1$

3. marigirl

so then i have: 2 cos^2(x)=cos(2x)+1

4. marigirl

when i integrate that I get sin(2x)/2 + x....... the ans says sin(x)cos(x)+x

5. anonymous

use trig identities for sin(2x)

6. anonymous

sin(2x) = 2sin(x)cos(x)

7. marigirl

thanks!

8. anonymous

: )

9. anonymous
10. anonymous

probs a good idea to have a cheat sheet by your side when you do these problems

11. anonymous

cheat sheet of trig identities...

12. marigirl

even the cheat sheet is complicated :(

13. anonymous

not if you know what you are looking for! if you find it hard to integrate something and its not your basic cosx sin(x) etc...then most likely its a trig identity you need to use to replace it

14. marigirl

or i just need to do more problems! haha

15. anonymous

yep, repitition and u will be a gun

16. marigirl