# Math Help - Another question about complex number in polar form

1. ## Another question about complex number in polar form

http://www.mathhelpforum.com/math-he...-new-post.html

Deveno given an example like what $(a+ai)(a-ai)=0$

Here another complex number discussion recently:
http://www.mathhelpforum.com/math-he...rm-184791.html

If rewrite two complex numbers to polar form and multiple with other one. I get a difference result: $2a^2$ (i.e. real part only)

What I'm missing?

2. ## Re: Another question about complex number in polar form

What you wright is true. I don't see any mistake:
$(a-ai)(a+ai)=(a)^2-(ai)^2=a^2-(a^2i^2)=a^2+a^2=2a^2$

Take an example:
$(3-4i)(3+4i)=9-(4i)^2=9-(-16)=25$

I don't see any problem ...