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

1. Mar 14, 2007

linuxux

1. The problem statement, all variables and given/known data

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.

3. The attempt at a solution

First thing that comes to mind is the eqaute the two, but i dont know how that helps me?

2. Mar 14, 2007

dextercioby

3. Mar 14, 2007

HallsofIvy

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

4. Mar 14, 2007

linuxux

thanks ive 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...

Last edited: Mar 14, 2007
5. Mar 14, 2007

Gib Z

6. Mar 14, 2007

linuxux

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

Last edited: Mar 14, 2007