Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 6 - Section 6.3 - Trigonometric Functions of Angles - 6.3 Exercises - Page 501: 75

Answer

Step 1. $cos\theta=|OP|$ Step 2. $tan\theta=|RQ|$ Step 3. $csc\theta=|OS|$ Step 4. $sec\theta=|OQ|$ Step 5. $cot\theta=|RS|$

Work Step by Step

Step 1. Use the figure provided with the Exercise, we have $cos\theta=\frac{|OP|}{|OR|}=|OP|$ (since |OR|=1) Step 2. $tan\theta=\frac{|PR|}{|OP|}$ since $\Delta OPR$ and $\Delta ORQ$ are similar triangle, we have $\frac{PR}{OP}=\frac{RQ}{OR}=RQ$, we have $tan\theta=|RQ|$ Step 3. $csc\theta=\frac{1}{sin\theta}=\frac{1}{|PR|}$, use the properties of similar triangles of $\Delta OPR$ and $\Delta ORS$, we have $\frac{PR}{OR}=\frac{OR}{OS}$ so that $\frac{1}{|PR|}=|OS|$ which means that $csc\theta=|OS|$ Step 4. $sec\theta=\frac{1}{cos\theta}=\frac{1}{|OP|}$, use the properties of similar triangles of $\Delta OPR$ and $\Delta ORQ$, we have $\frac{OP}{OR}=\frac{OR}{OQ}$ so that $\frac{1}{|OP|}=|OQ|$ which means that $sec\theta=|OQ|$ Step 5. $cot\theta=\frac{|OP|}{|PR|}$ since $\Delta OPR$ and $\Delta ORS$ are similar triangle, we have $\frac{OP}{PR}=\frac{RS}{OR}=RS$, we have $cot\theta=|RS|$
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