Question

Tentukan nilai dari sin 10 Sin 50 Sin 70
beserta penjabarannya

Answer 1

Verified answer

Jawab

sin 10 sin 50 sin 70  = ..

= (sin 70 sin 50) . sin 10
= - 1/2 { cos 120 - cos 20) . sin 10
= - 1/2 (-1/2 - cos 20) sin 10
= 1/4 sin 10  + 1/2 cos 20 sin 10
= 1/4 sin 10 + 1/4 [ 2 cos 20 sin 10]
= 1/4 sin 10 + 1/4 [sin 30 - sin 10]
= 1/4 sin 10 + 1/4 sin 30 - 1/4 sin 10
= 1/4 sin 30
= 1/4 (1/2)
= 1/8