If z1&z2 are two complex numbers and arg(z1+z2z1−z2)=π2 but |z1+z2|≠|z1−z2|, then the figure formed by the points represented by 0, z1,z2,z1+z2 is
If |Z1 + Z2| = |Z1| - |Z2| where Z1, Z2 are two non-zero complex numbers, then arg(Z1) - arg(Z2) is