# Math Help - trigonometry equation

1. ## trigonometry equation

cos2x+3sinx-1=0 , -pi<x<2pi (this is the range)

2. Originally Posted by jcfulton
cos2x+3sinx-1=0 , -pi<x<2pi (this is the range)
recall that $\cos 2x = 1 - 2 \sin^2 x$, so you have

$2 \sin^2 x -3 \sin x = 0$

which is another quadratic that you can deal with (hint: factor out sine)