Question

Need help solving Solving Trigonometric Equations.

Alright, so there are four questions: the only directions I am given is "Solve."

1. cosx+1=0 ; x∈R
2. 4sin^2 x-1=0 ; x∈R
3. 2cos^2 x+3cosx+1=0 ; 0≤x<2π
4. sin2x-2cosx=0 ; 0≤x<2π

I've worked out a few of the problems but just need to know if I'm right.


1) x =π+2πn

4) x=π/2+2πn and x=3π/2+2πn