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

Dec 30, 2014

Plotting the polar curve for $0 \le \theta \le 2 \pi$ I got:

I used Excel:
In the first column I put the angles in Radians;
In the second column is calculated $a \cdot \cos \left(4 \theta\right)$ 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: