If z1,z2,z3 and z4 be the consecutive vertices of a square, then z21+z22+z23+z24 equals
We know that, z2−z1z4−z1 = |z2−z1||z4−z1|eiP/2 = i (as |z2−z1| = |z4−z1|)
ϕ (z4−z1)2+(z2−z1)2 = 0
similarly z4−z3z2−z3 = i
ϕ (z4−z3)2+(z2−z3)2 = 0
On adding Eqs (i) and (ii), we get
2z21+z22+z23+z24−z1z2−z4z1−z4z3−z2z3 = 0
z21+z22+z23+z24 = z1z2+z2z3+z3z4+z4z1