Tentukan: Cos 75°.cos15°= Tolong bantuin donk

cos 75 x cos 15=
√6 - √2 / 4 x √6 + √2 / 4 = 1/4

2 cos 75.cos 15 = cos (75+15) + cos (75-15)
2 cos 75.cos15= cos (90) + cos (60)
2 cos 75.cos 15 = 0 + 1/2
cos 75.cos 15 =1/2 : 2
cos 75.cos 15 = 1/2 . 1/2
=1/4