Question

Cos 150 derajat senilai dengan?

Answer 1

Cos 150 = - cos (180 - 150)
= - cos 30
= - (akar 2 )/ 2

Answer 2

Cos 150 mengingat kuadran II.
cos(180-a) = -cos a
Mengambil a = 30
Didapat:
cos(180-30) = -cos 30
cos 150 = -cos 30
cos 150 = - 1/2 √3