Question

Solve 2 - 3 cos x = 5 + 3 cos x for 0° ≤ x ≤ 180°

a. 150°
b. 30°
c. 60°
d. 120°

Answer 1

The correct answer is Option d : 120°

Explanation:

First we bring all the cos x terms to one side

2 = 5 + 6 cos x

Now we bring all the numerals to one side

-3 = 6 cos x

-
`(1)/(2)` = cos x

∵ cos 60° =
`(1)/(2)` ∴ cos x = cos 60°

x = 60°

Now just flip over for the negative to get 180-60 = 120

∴ The answer is 120°.