Question

CAN YOU ANSWER DISS?

Answer 1

Answer:

B

Step-by-step explanation:

This is a quadratic in cosines

Factor by considering the factors of the product 2 × 1 = 2 which sum to give the coefficient of the cos x term (3 )

the factors are + 2 and + 1

use these factors to split the middle term

2cos²x + 2cosx + cosx + 1 = 0 (factor by grouping )

2cosx(cosx + 1) + 1(cosx + 1) = 0 (take out common factor (cosx + 1) )

(cosx + 1)(2cosx + 1) = 0

equate each factor to zero and solve for x

cosx + 1 = 0

cosx = - 1 ⇒ x = π

2cosx + 1 = 0

cosx = - $\frac{1}{2}$

since cosx < 0 then x is in second/ third quadrant

x = $\frac{2\pi }{3}$ or x = $\frac{4\pi }{3}$