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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
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The figure above shows the relationships between polar and quadratic
coordinates. From this figure we can derive the following relations:
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Thus, our 3-step strategy for plotting any polar equation shall be as follows:
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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.
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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.
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