

Plotting Polar Functions
Suppose you have a polar function in the form:
r = f ( ø )
where r is the length of line emerging from the origin to a point at an angle
of ø.
and you need to plot it using a C program. All we need to do is to simply use the methods
we used previously after converting polar coordinates into
quadratic ones.
Converting polar coordinates to quadratic coordinates and vice versa

The figure above shows the relationships between polar and quadratic
coordinates. From this figure we can derive the following relations:


Thus, our 3step strategy for plotting any polar equation shall be as follows:

1. Get the value of r corresponding to the various ø values (remember
that ø values in polar functions are always in radians not degress).
2. Convert the polar point (r , ø) into a quadratic point
(x , y). This is done by
the C functions P2Q_x() and P2Q_y()
in the code shown below.
3. Use the functions defined previously to plot the equation.

We shall now apply the above strategy to plot the function
r = sin(2ø) + 2 cos(3ø);
Here's the C program to do it.
Here's the result of this program
If you wish to download a compiled version of this program that can run under DOS/Windows
environments, click here (50 KB).
You will also need this file (5.5 KB) in the same folder as the executable.
