hitunglah nilai cos 105

jawab

cos 105 = cos (60 + 45)
= cos 60 cos 45 - sin 60 sin 45
= 1/2 . 1/2√2  -1/2 √3.  1/2√2
= 1/4 √2 - 1/4 √6
= 1/4 (√2 - √6)