Nilai dari sin 11π/6 + 2 cos 4π/3- sin 7π/6

Jawaban yang benar adalah -1. Sifat : π = 180° sin (360° - a) = - sin a cos (180° + a) = - cos a sin (180° + a) = - sin a cos 60° = ½ sin 11π/6 + 2 cos 4π/3 - sin 7π/6 = sin (11·180°/6) + 2 cos (4·180°/3) - sin (7·180°/6) = sin 330° + 2 cos 240° - sin 210° = sin (360° - 30°) + 2 cos (180° + 60°) - sin (180° + 30°) = - sin 30° + (- 2 cos 60°) - (-sin 30°) = - sin 30° - 2 cos 60° + sin 30° = -2 cos 60° = -2 · ½ = -1 Jadi, sin 11π/6 + 2 cos 4π/3 - sin 7π/6 = -1.