How to determine the point of intersection of sine and cosine?

[linuxux]

Homework Statement

Im not sure how to start this question: determine the points of intersection between y=sin x and y=cos 2 x for x between 0 and pi.

The Attempt at a Solution

First thing that comes to mind is the eqaute the two, but i don't know how that helps me?

 

[dextercioby]

It should help you. And the identities regarding the sin and cos functions should help you more...

 

[HallsofIvy]

Particularly an indentity that says cos(2x) is equal to something.

 

[linuxux]

thanks I've got it now, but is the only point of intersection in the range at \frac{\pi}{2}? i suppose i could graph it to be sure...

 

[Gib Z]

I just searched this in google, here you go:
http://mathcentral.uregina.ca/QQ/database/QQ.09.04/kris1.html

 

[linuxux]

okay, i was solving incorrectly, they will also both be at 30^{o}. i also assumed i would get a "nice" number. thanks.