Which Triangle?

Geometry Level 4

If $$\theta$$ is real and $${ z }_{ 1 }$$, $${ z }_{ 2 }$$ are connected by $${ z }_{ 1 }^{ 2 }+{ z }_{ 2 }^{ 2 }+2{ z }_{ 1 }{ z }_{ 2 }\cos { \theta } =0$$, then triangle with vertices $$0$$, $${ z }_{ 1 }$$ and $${ z }_{ 2 }\quad$$ is

×