sin 80° sin 40° sin 20°

Halo Raditya, kakak bantu jawab ya. Jadi jawaban soal di atas adalah 1/8. √3. Ingat konsep: 1. cos 60° = 1/2 2. cos (180°-x) = -cos x 3. -2 sin x sin y = cos (x +y) - cos (x- y) 4. 2cos x sin y = sin(x+ y) - sin(x-y) Dari soal akan dicari nilai sin 80° sin 40° sin 20°. Berdassarkan konsep di atas didapat: (sin 80° sin 40°) sin 20° = -1/2 (cos (80° + 40°)- cos ( 80° - 40°)) =-1/2 ( cos 120°- cos 40°)sin 20° =-1/2( cos(180° -60°) - cos 40°)sin 20° =-1/2 (- cos60° - cos40°)sin 20° =-1/2 (-1/2 -cos40°)sin 20° = 1/4 sin 20° +1/2 cos40°sin 20° =1/4 sin 20° +1/2. 1/2 . (sin(40°+ 20° )-sin(40°- 20° )) =1/4 sin 20° +1/4(sin60°-sin 20°- 20° ) =1/4 sin 20° +1/4(1/2√3 -sin20° ) =1/4 sin 20° +1/4(1/2√3- sin 20° ) =1/4 sin 20° -1/4 sin 20° + 1/8. √3 = 0 + 1/8. √3 =1/8. √3 Jadi sin 80° sin 40° sin 20°=1/8. √3. Semoga membantu ya: )