100 POINTS AND BRAINLIEST!! PRE CALC! The trigonometric relation cos (π/3 + x) + cos (π/3 - x) is equivalent to:

a. cos 2x
b. cos x
c. sin x
d. 1/2 cos x

Please explain your answer :)

b

Step-by-step explanation:

use cos(r + s ) = cosrcoss - sinrsins to expand.

cos pi/3 cosx - sin pi/3 sinx + cos pi/3 cosx + sin pi/3 sinx

the two in bold cancel out.

cospi/3 cosx + cospi/3 cosx

pi = 180° in trigonometry.

cos 180/3 cosx + cos 180/3 cosx

1/2 cosx + 1/2 cosx

= cos x

x = 2

step-by-step explanation:

if sr parallel to ba then the sides bc and ac are in proportion, that is

= ← substitute values

= ( cross- multiply )

27x = 6(4x + 1)

27x = 24x + 6 ( subtract 24x from both sides )

3x = 6 ( divide both sides by 3 )

x = 2