Question

cos(120°+A) + cos(120°-A) = -cosA

answer is -cosA I want solution please answer fast and correct &fast please let me know this in google not coming guys all are getting wrong answer is -Cos A I want correct solution and answer please do it correct
​ please answer fast and correct ​

Answer 1

Step-by-step explanation:

cos(120° + A) + cos(120° - A)

[∴ cos(a + b) + cos(a - b) = 2 cos a cos b]

⇒ 2 cos (120) * cos A

⇒ 2 cos(90° + 30°) * cos A

[∴ cos(90° + Ф) = -sinФ]

⇒ - 2 sin 30° * cos A

⇒ - 2(1/2) * cos A

⇒ - cos A

Hope it helps!Brainliest it sister!