Thinking Mathematically (6th Edition)

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

Chapter 10 - Geometry - 10.1 Points, Lines, Planes, and Angles - Exercise Set 10.1 - Page 618: 77

Answer

The pair of complementary angles is \[\measuredangle 1\]and\[\measuredangle 5\].

Work Step by Step

It is known that two angles are said to be complementary when the sum of two angles is equal to 90°. Now the pairs of angles in the figure that are complementary are as follows: \[\measuredangle 1\]and\[\measuredangle 2\], \[\measuredangle 4\] and \[\measuredangle 5\]and\[\measuredangle 4\], \[\measuredangle 1\] and \[\measuredangle 5\]and\[\measuredangle 2\]and\[\measuredangle 4\]. The sum of \[\measuredangle 1\] and \[\measuredangle 2\] will be 90°as \[\measuredangle 1\], \[\measuredangle 2\] and \[\measuredangle 3\] constitutes a straight line the sum of which is 180°. Now the sum of \[\measuredangle 1\] and \[\measuredangle 2\] will be as follows: \[\begin{align} & \measuredangle 1+\measuredangle 2+\measuredangle 3=180{}^\circ \\ & \measuredangle 1+\measuredangle 2+90{}^\circ =180{}^\circ \\ & \measuredangle 1+\measuredangle 2=90{}^\circ \end{align}\] Thus, sum of\[\measuredangle 1\] and \[\measuredangle 2\] is 90°. Similarly, the sum of \[\measuredangle 4\] and \[\measuredangle 5\] will be as follows: \[\begin{align} & \measuredangle 4+\measuredangle 5+\measuredangle 6=180{}^\circ \\ & \measuredangle 4+\measuredangle 5+90{}^\circ =180{}^\circ \\ & \measuredangle 4+\measuredangle 5=180{}^\circ -90{}^\circ \\ & =90{}^\circ \end{align}\] Thus, the sum of \[\measuredangle 4\] and \[\measuredangle 5\] is 90° Similarly, the sum of \[\measuredangle 2\] and \[\measuredangle 4\]will be as follows: \[\begin{align} & \measuredangle 2+\measuredangle 3+\measuredangle 4=180{}^\circ \\ & \measuredangle 2+90{}^\circ +\measuredangle 4=180{}^\circ \\ & \measuredangle 2+\measuredangle 4=180{}^\circ -90{}^\circ \\ & \measuredangle 2+\measuredangle 4=90{}^\circ \end{align}\] In the same manner the sum of \[\measuredangle 1\] and \[\measuredangle 5\] will be as follows: \[\begin{align} & \measuredangle 1+\measuredangle 5+\measuredangle 6=180{}^\circ \\ & \measuredangle 1+\measuredangle 5+90{}^\circ =180{}^\circ \\ & \measuredangle 1+\measuredangle 5=180{}^\circ -90{}^\circ \\ & =90{}^\circ \end{align}\] \[\measuredangle 1\]and\[\measuredangle 5\] are complimentary angles. Thus, option d seems to be the correct choice and rest options are in correct.
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