Click the Graphics|New|Polar Graph command to create this kind of graphs. This will cause the Polar Graph dialog box show where you can modify it's properties (formula, color, width and style, intervals and so on).

Polar Graph Dialog box

The R(t) = box prompt you to enter a function's formula respectively to the parameter t. The right hand side of the formulas must be any mathematical expression including constants and an independent variable (parameter).

The Parameter tab lets you setup the parameter for a polar graph (set its ranges and its step). Be attentive while manipulating these values. Setting too small step or too wide range causes growth of number of calculations. This may consume much time while building a parametric graph.

The Visible option allows you to temporarily hide a graph without deleting it from the project.

The Intervals tab lets you to choose the space for each line. This makes it possible to draw lines that only occupie part of the (x, y)-axes (not the whole as by default).

Use the Color and Size boxes on the right to adjust the color and the thickness of the curve.