1. ## cosine equation

Having a bit of a problem solving this

cos2x = 3sinx +2

thanks

2. Originally Posted by echo123
Having a bit of a problem solving this

cos2x = 3sinx +2

thanks
Substitute $\cos(2x) = 1 - 2 \sin^2 x$ and re-arrange into a quadratic equation in sin x. Factorise. Use the null factor law. That should leave you with:

$(2 \sin x + 1) (\sin x + 1) = 0 \Rightarrow \sin x = - \frac{1}{2} \,$ or $\, \sin x = -1$.

One difficult trig equation to solve becomes two simple trig equations to solve ......