When 0° < θ < 90°, solve the following equation:

2 cos² θ + sin θ - 2 = 0

When 0° < θ < 90°, solve the following equation:

3 cos θ = 2 sin² θ

When 0° < θ < 90°, solve the following equation:

sec² θ - 2 tan θ = 0

When 0° < θ < 90°, solve the following equation:

tan² θ = 3 (sec θ - 1).