Question

The value
of cos 27° +cos 93°
+cos 147 is​

Answer 1

Answer:

cos27°+cos93°+cos147°

=2cos(27°+93°)/2cos(27°-93°)/2+cos147°

=2cos60°cos33°+cos(180°-33°)

=2×1/2cos33°+cos{(90°×2)-33°}  [∵, cos60°=1/2 and cos(180°-Ф)=-cosФ]

=cos33°+(-cos33°)

=cos33°-cos33°

=0 (Proved)