Thinking Mathematically (6th Edition)

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

Chapter 10 - Geometry - 10.3 Polygons, Perimeter, and Tessellations - Exercise Set 10.3 - Page 638: 64

Answer

The measure of an angle 1 in a 5-sided polygon is\[65{}^\circ \].

Work Step by Step

A measure of an angle of an irregular polygon will be determined by adding all the interior angles and subtract from the sum of the measures of all 5 angles. The sum of the measures of the angles will be determined by using the formula\[\left( n-2 \right)\times 180{}^\circ \]. The sides of the polygon, n is 5. Compute the sum of the angles of a polygon with 5 sides as shown below: \[\begin{align} & \text{Sum of angles}=\left( n-2 \right)\times 180{}^\circ \\ & =\left( 5-2 \right)\times 180{}^\circ \\ & =3\times 180{}^\circ \\ & =540{}^\circ \end{align}\] Sum of interior angles of a polygon. The corresponding interior and exterior angles make a straight line, which is\[{{180}^{o}}\]. Compute the sum of interior angles as follows: \[\begin{align} & \text{sum of angles}=140{}^\circ +135{}^\circ +\left( 180{}^\circ -97{}^\circ \right)+\left( 180{}^\circ -63{}^\circ \right) \\ & =140{}^\circ +135{}^\circ +83{}^\circ +117{}^\circ \\ & =475{}^\circ \end{align}\] Compute the measurement of angle 1 as follows: \[\begin{align} & m\measuredangle 1=540{}^\circ -475{}^\circ \\ & =65{}^\circ \end{align}\]
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