Question

6 sin² x - sin x - 1 = 0. maka, cos x = ..?

Answer 1

Faktorkan saja
6 sin² x - sin x - 1 = 0
(3sin x + 1)(2sin x - 1) = 0
sin x = -1/3 ⇒ cos x = - 2/3 √3
sin x = 1/2 ⇒ cos x = √5 /2

Answer 2

6 sin² x - sin x - 1 = 0dimisalkan sin x =a
jadi 6a^2 -a-1=0
(3a+1)(2a-1)=0
a= -1/3 atau a = 1/2
sin x =1/2
x= 30 derajat
cos 30 =1/2