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Test for symmetry and then graph each polar equation. $$r \cos \theta=-3$$

Short Answer

Expert verified
The polar equation \(r \cos \theta=-3\) is symmetric with respect to the pole, but not the polar axis. The graph of this equation represents a vertical line passing through -3 on the x-axis.

Step by step solution

01

Testing for symmetry

For \(r \cos \theta=-3\), go ahead and replace \(-r\) for \(r\) and \(-\theta\) for \(\theta\). The result is \(-r \cdot \cos(-\theta) = -3\). Due to the even symmetry of the cosine function, we get \(-r \cos \theta=-3\). This polar equation changes, so it's not symmetric about the polar axis.
02

Testing for pole symmetry

Replace \(\theta\) with \(-\theta\) in the original equation: \(r \cos(-\theta) = -3\), which simplifies to \(r \cos \theta = -3\). The equation doesn't change, so the graph is symmetric with respect to the pole.
03

Graphing the function

To graph \(r \cos \theta=-3\), recall that its rectangular form is \(x=-3\). This represents a vertical line cutting the x-axis at -3. In polar coordinates, it's an entire line going through pole (-3,0) and extending to the negative and positive direction of the y-axis. Graph the line on the coordinate system.

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