Math Editor

Q. cos(180°−A)+cos(180°+B)+cos(180°+C)−sin(90°+D)

⇒cos(22π​−A)+cos(22π​+B)+cos(22π​+C)−sin(2π​+D)

→−cosA−cosB−cosC−cosD

→−cos(22π​−B)−cosB−cos(22π​−D)−cosD

→cosB−cosB+cosD−cosD

→0Proved.

By: Dipankar Sadhukhan.