Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 10 - Geometry - 10.4 Area and Circumference - Exercise Set 10.4 - Page 648: 33

Answer

The area of the shaded region of the given figure, in terms of \[\pi \] is\[\left( \text{12}\text{.5}\pi -24 \right)in{{.}^{2}}\].

Work Step by Step

We have to find the area of the shaded region in the given figure. In the figure, a right angled triangle is within the bigger circle. The area of the shaded region can be found out by subtracting the area of the triangle, with base equal to \[6\text{ inches}\] and the height equal to \[\text{8 inches}\],from the area of the circle. Compute the diameter of the circle by applying the Pythagoras theorem to the right angled triangle, as follows: \[\begin{align} & d=\sqrt{8\text{ i}{{\text{n}}^{2}}+6\text{ i}{{\text{n}}^{2}}} \\ & =\sqrt{100\text{ in}} \\ & =10\text{ in} \end{align}\] So, the radius will be half of the diameter, that is \[\frac{10\text{ inches}}{2}=5\text{ inches}\]. According to this formula, the area of the semicircle, with radius equal to \[5\text{ inches}\] will be: \[\begin{align} & {{A}_{1}}=\frac{1}{2}\pi {{r}^{2}} \\ & =\frac{1}{2}\pi \times 5\text{ in}{{\text{.}}^{2}} \\ & =12.5\pi \text{ in}{{\text{.}}^{2}} \end{align}\] The area of the triangle, with base equal to \[6\text{ inches}\] and the height equal to \[\text{8 inches}\]will be: \[\begin{align} & {{A}_{2}}=\frac{1}{2}bh \\ & =\frac{1}{2}\times 6\text{ in}\text{.}\times 8\text{ in}\text{.} \\ & =24\text{ in}{{.}^{2}} \end{align}\] The area of the shaded region will be: \[\begin{align} & A={{A}_{1}}-{{A}_{2}} \\ & =\left( \text{12}\text{.5}\pi -24 \right)in{{.}^{2}} \end{align}\] Hence, the area of the shaded region of the given figure, in terms of \[\pi \] is\[\left( \text{12}\text{.5}\pi -24 \right)in{{.}^{2}}\]
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