Question

Jawaban dari nilai cos 195 + cos 105 adalah

Answer 1

Cos 195° + cos 105°
= 2 cos 1/2 (195° + 105°) cos 1/2 (195° - 105°)
= 2 cos 1/2 (300°) . cos 1/2 (90°)
= 2 cos 150° cos 45°
= 2 . -cos 30° . cos 45°
= 2 . -1/2 √3 . 1/2 √2
= - 1/2 √6