If one of the lines of $m y ^ { 2 } + \left( 1 - m ^ { 2 } \right) x y - m x ^ { 2 } = 0$ is a bisector of the angle between the lines $x y = 0$, then $m$ is (1) $- 1 / 2$ (2) - 2 (3) 1 (4) 2
If one of the lines of $m y ^ { 2 } + \left( 1 - m ^ { 2 } \right) x y - m x ^ { 2 } = 0$ is a bisector of the angle between the lines $x y = 0$, then $m$ is\\
(1) $- 1 / 2$\\
(2) - 2\\
(3) 1\\
(4) 2