Thread: I need help solving this trig problem

I have to determine the angle that satisfies the following equation:

cos(x)=-2tan(x)

All I have managed to do is reexpress this as:

(cos(x))^2 + 2sin(x) = 0

However, I don't think this helps me? I am quite stuck with this problem and am not sure how to approach it. A worked solution would be greatly appreciated.

If you replace (cos(x))^2 by 1 - (sin(x))^2, you will get a quadratic equation on sin(x).

Thank you very much for your reply