Polar curves are graphs that use polar coordinates instead of the usual x and y coordinates. Each point is described by a distance from the center, called the radius, and an angle measured from the positive x-axis. The relationship is written as r equals some function of theta. This way of plotting makes it easier to describe shapes that have natural symmetry around a center point. For instance, a circle centered at the origin can be written simply as r = 2, and a spiral can be written as r = th