Free ebook http://tinyurl.com/EngMathYT I discuss and solve an example where it is required to show that $$Re [(1-z)/(1+z)] = 0$$ for all complex numbers $z$ with $|z|=1$. The method involves a simple application of a basic identity. Such an example is seen in 1st year university mathematics. Note, I am experimenting with a different (lapel-style) mic in this video (-18Db)