8 cos 15° sin75° ????

jawab
8 cos 15 sin 75 = 4 (2 sin 75 cos 15)
= 4 { sin 1/2 (75+15) + sin 1/2 (75-15)}
= 4 { sin 45 + sin 30)
= 4 ( 1/2 √2 + 1/2)
= 2√2  + 2