a) 2 sin 15° cos 15° =....... b) sin 10° cos 20° + sin 20° sin 10° =.... c) cos 75° cos 15° + sin 75° sin 15° = ...... bantuan

2sin15 cos 15
= sin ( 15+15) + sin (15-15)
= sin 30 + sin 0
= 1/2

Sin10cos20 + sin20sin10
=1/2(sin (10+20) +sin(10-20))+ (-1/2) (cos (20+10) -cos ( 20-10))
= 1/2 (sin30+sin10) -1/2(cos30 - cos 10)
=1/2(1/2+sin10) -1/2 (1/2akar3 - cos10)
=1/4 + 1/2sin 10 -1/4akar3+cos 10

Cos75cos15 +sin75sin 15
=1/2(sin90-sin60) -1/2 (cos90-cos60)
=1/2(1-1/2akar3) - 1/2 ( 0-1/2)
=1/2-1/4akar3+1/4
=3/4 - 1/4akar 3


Maaf kalau salah