In Example 4, change cos to sin. Data from Example 4 Plot the graph of r = 2cos2. In finding values of r, we must

In Example 4, change cos to sin.

Data from Example 4

Plot the graph of r = 2cos2θ.
In finding values of r, we must be careful first to multiply the values of θ by 2 before finding the cosine of the angle. Also, for this reason, we take values of θ as multiples of π/12, so as to get enough useful points. The table of values follows:

For values of θ starting with π, the values of θ repeat. We have a four-leaf rose, as shown in Fig. 21.115.

r 2 1.7 1 0 -1 -1.7 T 7 T2 r -1.7 -1 0 1 1.7 2 2 3 Sm 6 11 T -2