Q:

complex numbers. help in proof that $e^{-it}=1/e^{it}$

I need to show that $e^{-it}=\frac{1}{e^{it}}$. 
but I don't understand what needs to be proven, it seems trivial to me. If anyone could help me. 
Is the claim true even if t is not real?
Thank you

A:

You have$$e^{it}\cdot e^{-it}=e^{it-it}=e^0=1$$and therefore$$e^{-it}=\frac1{e^{it}}.$$

