2 co$s^2$θ − 3 cos θ + 1 = 0 and 0° < θ < 90°. Find θ.

(2 cos θ − 1)(cos θ − 1) = 0 gives cos θ = 1/2 or 1. cos θ = 1 means θ = 0°, which is excluded, so θ = 60°.