1) cos(x-30)=3cos(x+30) find x for 0<x<360 degrees
2) 4tan2xtanx=1 find x for 0<x<2pi in radians
thanks
For the first problem, use the angle sum identities for cosine. $\displaystyle \cos (x - 30) = \cos x \cos 30 + \sin x \sin 30$ and $\displaystyle \cos (x + 30) = \cos x \cos 30 - \sin x \sin 30$. You should be able to simplify the original equation to $\displaystyle 4 \sin x \sin 30 = 2 \cos x \cos 30$ and work it from there.