cos theta + cos (120° +theta) + cos (120° - theta)
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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 hence proved....
Step-by-step explanation:
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