# How do you graph the function #r^2 = 9cos(2θ)#?

##### 1 Answer

Nov 17, 2016

I have inserted the graph of this Lemniscate, using the Socratic facility for the cartesian frame.

#### Explanation:

The period of

period can be chosen as

wherein

As

initial line.

Also, as cos (2(pi-theta) = cos 2theta, the graph is symmetrical

about the vertical

A Table for half period

Use symmetry. for the other three quarters..

graph{(x^2+y^2)^2=9(x^2-y^2) [-10, 10, -5, 5]}