Chapter 10 - Parametric Equations and Polar Coordinates - 10.3 Exercises - Page 687: 10

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The region contains points whose distance from the origin is between 1 and 3 (arcs included), and terminal ends to the angles to these points are between $\displaystyle \theta=\frac{\pi}{6}$ and $\displaystyle \theta=\frac{5\pi}{6}$, excluding the border line segments.