Math, asked by lumbini41, 10 months ago

cos A + cos (120° + A) + cos (120° -A)=

Answers

Answered by inayathussain53651

2

cos A+ cos(120°+A)+cos(120°-A)

=Cos A + 2 Cos {(120° + A+ 120°- A)/2} cos{120°+A-120°+A)/2..........(1)by using the formula

Cos C + cos D = 2 Cos (C+D)/2cos(C-D)/2

(1) reduces to Cos A + 2 cos 120°cos A

= Cos A+2 (-1/2) cos A

=0

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