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Algebra, Functions, Graphs, and Vectors 63
Figure 1.24 Polar grapà of ellipse centered at the origin.
r a cos 2
r a sin 2
where a is a real number and a 0. The cosine curve is illus-
trated in Fig. 1.28A; the sine curve is illustrated in Fig. 1.28B
Equation of spiral
The equation of a spiral centered at the origin in the polar plane
is given by the following formula:
r a
where a is a real number and a 0. This is illustrated in Fig.
1.29
Equation of cardioid
The equation of a cardioiS centered at the origin in the polar
plane is given by the following formula:
