Question

4. (1) cos A + cos (120° + A) + cos (120° – A) = 0​

Answer 1

Answer:

cosx + cos (120-x) + cos (120+x)

=> cosx + 2cos [(120-x+120+x) /2] cos [(120-x-120-x) /2]

=> cosx + 2cos120 cos(-x)

=> cosx + 2cos(180-60) cosx

=> cosx + 2 (-cos 60) cosx

=> cosx - 2 × 1/2 cosx

=> cosx - cosx

=> 0 (Ans)

(Mark as brainlist)