Vertical velocity = 30 × sin(30°) = 30 × 0.5 = 15 m/s. At maximum height, final vertical velocity = 0. Using v² = u² − 2gh → 0 = 15² − 2×9.8×h → 225 = 19.6h → h = 225 / 19.6 ≈ 11.48 m.