Question

Sin a = - 1/2√3 . interval 180° < a > 270° . nilai cos a ?

Answer 1

Sin a = -sin 60
Maka,
sin a = sin(-60)

Solusi 1:
a = -60 + 360 = 300

Solusi 2:
a = 180-(-60) = 240

Diambil a = 240
Didapat:
cos 240 = cos(180+60)
cos 240 = -cos 60
cos 240 = - 1/2
cos a = -1/2