Archimedean spiral

The Archimedean spiral is a spiral named after the Greek mathematician Archimedes. It can be described by the equation:

Archimedean spiral is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

$\,r=a+b\theta$

with real numbers a and b.

Draw an Archimedean spiral.