Question

x=y cos 180°=zcos 240°

Answer 1

Firstly take x=y cos(180°)
x=y cos(90°)+cos(90°)
x=y (0)
x=0

Secondly take x=z cos(240°)
x=z cos(60°)+cos(60°)+cos(60°)+cos(60°)
x=z 1/2 + 1/2 + 1/2 + 1/2
x=z 4/2
x=2z