Question

2cos^2x - 3sinx=0

Answer 1

Do you mean \[2\cos^2(x)-3\sin(x)=0\]?
If that's the case, then use sin^2(x)+cos^2(x)=1, so cos^2(x)=1-sin^2(x)
Then 2(1-sin^2(x))-3sin(x)=0
This is a simple quadratic equation which I think you can solve. :)