In the diagram, < WOZ = 180\(^o\) (angle on a straight line) < WOX = < XOY = < YOZ (|WX| = |XY| = |YZ|) \(\frac{180^o}{3}\) = 60\(^o\) = 60\(^o\) M + m =2m (base angles of isosceles \(\bigtriangleup\), |OY| and |OZ| are radii) < YOZ + 2m (base angles of a \(\bigtriangleup\)) 60\(^o\) + 2m = 180\(^o\) (sum of a \(\bigtriangleup\)) 60\(^o\) + 2m = 180\(^o\) 2m = 180\(^o\) - 60\(^o\) 2m = 120\(^o\) m = \(\frac{120^o}{2}\) = 60\(^o\)