How solve a trigometric function

Hey everybody.

I have the following trig function and I have to simplify it so that it will only have sintheta in it. Can you show me how to do that?:

9.78049(1+0.005288sinsquaredx - 0.000006sinsquared2x) (m/ssquared)

**I tried pulling out a sinx, but that only seemed to complicate the problem because once I did that had to simplify the sin2x and I just couldn't find a way to do it!**

*Is there another way to approach this problem? I've exhausted all sources and my book has the most basic concepts possible!*

Any help is appreciated,

Stealth