Thinking Mathematically (6th Edition)

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

Chapter 10 - Geometry - 10.2 Triangles - Exercise Set 10.2 - Page 626: 9

Answer

The measurement of angle 1 is \[55{}^\circ \], angle 2 is \[65{}^\circ \], angle 3 is \[60{}^\circ \], angle 4 is \[65{}^\circ \], angle 5 is \[60{}^\circ \], angle 6 is \[120{}^\circ \], angle 7 is \[60{}^\circ \], angle 8 is \[60{}^\circ \], angle 9 is \[55{}^\circ \], and angle 10 is\[55{}^\circ \].

Work Step by Step

Compute the measurement of angle 1 using the fact that vertically opposite angles are equal to each other. Thus, \[\text{m}\measuredangle 1=55{}^\circ \]. Compute angle 7 using the fact that angles \[120{}^\circ \] and angle 7 form a straight angle. Therefore, their sum is equal to \[180{}^\circ \]. \[\text{m}\measuredangle 7+120{}^\circ =180{}^\circ \] Compute the measurement of angle 1 by subtracting \[120{}^\circ \]from both the sides of equation. \[\begin{align} & \text{m}\measuredangle 1=180{}^\circ -120{}^\circ \\ & \text{m}\measuredangle 1=60{}^\circ \\ \end{align}\] Compute the measurement of angle 8 using the fact that vertically opposite angles are equal to each other: \[\text{m}\measuredangle 8=\text{m}\measuredangle 7\]. Thus, \[\text{m}\measuredangle 8=60{}^\circ \]. Compute the measurement of angle 6 using the fact that vertically opposite angles are equal to each other. Thus, \[\text{m}\measuredangle 6=120{}^\circ \]. Compute the measurement of angle 5 using the fact that alternate angles are equal to each other: \[\text{m}\measuredangle 5=\text{m}\measuredangle 7\]. Thus, \[\text{m}\measuredangle 5=60{}^\circ \]. Compute angle 4 using the fact that angles\[55{}^\circ \], angle 4, and angle 5 forms a straight angle. Therefore, their sum is equal to \[180{}^\circ \]. Sum of all the three angels of a triangle is \[180{}^\circ \]. \[\begin{align} & 55{}^\circ +\text{m}\measuredangle 4+\text{m}\measuredangle 5=180{}^\circ \\ & 55{}^\circ +\text{m}\measuredangle 4+60{}^\circ =180{}^\circ \\ & \text{m}\measuredangle 4=180{}^\circ -115{}^\circ \\ & \text{m}\measuredangle 4=65{}^\circ \end{align}\] Compute the measurement of angle 2 using the fact that vertically opposite angles are equal to each other: \[\text{m}\measuredangle 2=\text{m}\measuredangle 4\]. Thus, \[\text{m}\measuredangle 2=65{}^\circ \]. Compute the measurement of angle 3 using the fact that vertically opposite angles are equal to each other: \[\text{m}\measuredangle 3=\text{m}\measuredangle 5\]. Thus, \[\text{m}\measuredangle 3=60{}^\circ \]. Compute the measurement of angle 9 using the fact that alternate angles are equal to each other. Thus, \[\text{m}\measuredangle 9=55{}^\circ \]. Compute the measurement of angle 10 using the fact that vertically opposite angles are equal to each other: \[\text{m}\measuredangle 10=\text{m}\measuredangle 9\]. Thus, \[\text{m}\measuredangle 10=55{}^\circ \]. Hence, the measurement of angle 1 is \[{{55}^{{}^\circ }}{}^\circ \], angle 2 is \[65{}^\circ \], angle 3 is \[60{}^\circ \], angle 4 is \[65{}^\circ \], angle 5 is \[60{}^\circ \], angle 6 is \[120{}^\circ \], angle 7 is \[60{}^\circ \], angle 8 is \[60{}^\circ \], angle 9 is \[55{}^\circ \], and angle 10 is \[55{}^\circ \].
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