What is the graph of #r=a cos 4theta#?

1 Answer
Dec 30, 2014

Plotting the polar curve for #0<=theta<=2pi# I got:
enter image source here
I used Excel:
In the first column I put the angles in Radians;
In the second column is calculated #a*cos(4theta)# for #a=2#;

The next two columns contain the corresponding values of x and y to plot your equation on a rectangular coordinate system x,y.

To obtain the values in the x and y columns you must remember the relationship between polar (first two columns) and rectangular (second two columns) coordinates:
enter image source here