# Math Help - Pre-Calc Graphing with Complex numbers. Multiplying with complex numbers.

1. ## Pre-Calc Graphing with Complex numbers. Multiplying with complex numbers.

One question I need help with.

If z=cisθ = r(cosθ + isinθ), show that (1/z) = (1/r)cis(-θ)

2. You can use the following facts to prove it.
$\begin{array}{l}
z = r\left[ {cis\left( \theta \right)} \right] \\
\bar z = r\left[ {cis\left( { - \theta } \right)} \right] \\
\end{array}$

$\frac{1}{z} = \frac{{\bar z}}{{\left| z \right|^2 }}$