Question

cosa +cos(120°+a)+cos (120°-a)=0

Answer 1

Hey dear hear is ur answer *********
_____________________

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@@@@@#####