(a) complete the table for the polar function and (b) plot the corresponding points. r = 2 cos 2θ (a) for…

(a) complete the table for the polar function and (b) plot the corresponding points. r = 2 cos 2θ (a) for each value of θ, find the corresponding value of r = 2 cos 2θ. (simplify your answers.) θ 0 π/4 π/2 3π/4 π 5π/4 3π/2 7π/4 r 0 0 0 0 0 0
Answer
Explanation:
Step1: Substitute $\theta = 0$
$r = 2\cos(2\times0)=2\cos(0)=2\times1 = 2$
Step2: Substitute $\theta=\frac{\pi}{2}$
$r = 2\cos(2\times\frac{\pi}{2})=2\cos(\pi)=2\times(- 1)=-2$
Step3: Substitute $\theta=\pi$
$r = 2\cos(2\pi)=2\times1 = 2$
Step4: Substitute $\theta=\frac{3\pi}{2}$
$r = 2\cos(2\times\frac{3\pi}{2})=2\cos(3\pi)=2\times(-1)=-2$
Step5: Substitute $\theta=\frac{7\pi}{4}$
$r = 2\cos(2\times\frac{7\pi}{4})=2\cos(\frac{7\pi}{2})=2\times0 = 0$
Answer:
| $\theta$ | $0$ | $\frac{\pi}{4}$ | $\frac{\pi}{2}$ | $\frac{3\pi}{4}$ | $\pi$ | $\frac{5\pi}{4}$ | $\frac{3\pi}{2}$ | $\frac{7\pi}{4}$ |
|---|---|---|---|---|---|---|---|---|
| $r$ | $2$ | $0$ | $- 2$ | $0$ | $2$ | $0$ | $-2$ | $0$ |