cosa +cos(120°+a)+cos (120°-a)=0
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Hey dear hear is ur answer *********
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cosa+{cos(120°+a)+cos(120°-a)}
=cosa+2×{cos(120°+a+120°-a)/2}×{cos(120°+a-120°+a)/2}
=cosa+2cos120°cosa
=cosa+2cos(90°×1+30°)cosa
=cosa+2(-sin30°)cosa
=cosa-2×(1/2)cosa
=cosa-cosa
=0[Proved]
Hope it will help u@@@@@#####
_____________________
cosa+{cos(120°+a)+cos(120°-a)}
=cosa+2×{cos(120°+a+120°-a)/2}×{cos(120°+a-120°+a)/2}
=cosa+2cos120°cosa
=cosa+2cos(90°×1+30°)cosa
=cosa+2(-sin30°)cosa
=cosa-2×(1/2)cosa
=cosa-cosa
=0[Proved]
Hope it will help u@@@@@#####
soh2:
please mark it as brainliest
many many thanks to u
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