The
polar coordinate system is an alternative to
Cartesian coordinates
for representing
position in a
plane. Instead of the (x,y) coordinates
most people are more familiar with, points are represented by (r,
theta)
coordinates; r being the
distance on a
straight line to the
origin, and
theta the
angle, usually in
radians, between that straight line and
another line from the origin that is designated the 0 angle.
The angles are
always measured in the same direction; an angle measured in the opposite
direction would be a negative angle. The theta coordinate is cyclic;
adding 2pi to it gives the same point. Usually polar coordinates are written
with the thetas constrained to an interval 0 to 2pi or -pi to pi, but in
some contexts the "wrapping around" of the theta coordinate is used;
for instance, in the graph of the spiral represented by the equation
r=theta.
The r is normally limited to non-negative numbers, but negative r is
sometimes used to represent a point at an angle pi apart from the theta
specified.
The nrt strikes again!