number. In polar coordinates, a complex number *z* is defined by the
modulus *r* and the phase angle *phi*. The modulus *r* is the distance
from *z* to the origin, while the phase *phi* is the counterclockwise
-angle from the positive x-axis to the line segment that joins the
-origin to *z*.
+angle, measured in radians, from the positive x-axis to the line
+segment that joins the origin to *z*.
The following functions can be used to convert from the native
rectangular coordinates to polar coordinates and back.