anonymous one year ago I need explanation...

1. anonymous

|dw:1439109817446:dw|

2. hartnn

know the double angle formula? cos 2x = ... ?

3. hartnn

in terms of cos^2 x

4. anonymous

No i dont

5. hartnn

ok, its good to know all variations of cos 2x formula I will write the 3 most important ones for you $$\Large \cos 2x = \cos^2 x - \sin^2 x$$ $$\Large \cos 2x = 2\cos^2 x - 1$$ $$\Large \cos 2x = 1-2\sin^2 x$$

6. hartnn

we need to use the 2nd one for our problem try to get expression for cos^2 x from it

7. anonymous

oh alright we are allowed to have a formula page. It says cos^2 x =1+cos2/2

8. hartnn

exactly, that you'll get from the 2nd formula, just plug that into your integral!

9. anonymous

|dw:1439110177783:dw|

10. anonymous

Alright this wasnt so bad! Thank you :)

11. hartnn

welcome ^_^

12. hartnn

|dw:1439110246947:dw|

13. anonymous

thanks cant forget the c.