Solve each equation for 0<_ 0<_ 2pi(3.14)

Question

A) 2cos^20 - sin0 -1=0

Answer 1

2cos^2 Ø - sinØ -1=0
2(1-sin^2 Ø) - sinØ - 1 = 0
-2sin^2 Ø - sinØ +1 = 0
2sin^2 Ø + sinØ - 1 = 0
(2sinØ + 1)(sinØ - 1) = 0

sinØ = -1/2 or sinØ = 1

case1: sinØ = -1/2
Ø must be in quads III or IV
Ø = 210 or Ø = 330°
or
Ø = 7π/6 or 11π/6

case2:
sinØ = 1
Ø = π/2

Answer 2

solve for theta:2cos(2theta-pi)= -2 ,for -2pi less or equal to theta less than 2pi