Hello,

You're saying that which is wrong : if the LHS equals 0 and the RHS equals . I don't think there is a rule that tells us how to expand .

However, I'm sure you know that if is a complex number then so

Take a look at equation #10 of Parallelogram -- from Wolfram MathWorld. It looks like the one you're asked to show, doesn't it ?I don't know how to interpret this result geometrically though, any help would be appreciated.