Provide an Appropriate Response $r = \frac { 1 - a \cos \theta } { 1 + a \cos \theta }$

Essay

Provide an appropriate response.
-Consider the curves corresponding to polar equations of the form $r = \frac { 1 - a \cos \theta } { 1 + a \cos \theta }$ where $a > 0$ . Explain how the graph changes as a changes. Identify any values of a for which the basic shape of the curve changes.