Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 7 - Section 7.1 - Trigonometric Identities - 7.1 Exercises - Page 543: 59

Answer

$\dfrac{(\sin t+\cos t)^{2}}{\sin t\cos t}=2+\sec t\csc t$

Work Step by Step

$\dfrac{(\sin t+\cos t)^{2}}{\sin t\cos t}=2+\sec t\csc t$ On the left side of the equation, evaluate the power in the numerator: $\dfrac{\sin^{2}t+2\sin t\cos t+\cos^{2}t}{\sin t\cos t}=2+\sec t\csc t$ Substitute $\sin^{2}t+\cos^{2}t$ with $1$ in the numerator: $\dfrac{1+2\sin t\cos t}{\sin t\cos t}=2+\sec t\csc t$ Rewrite the fraction on the left as $\dfrac{1}{\sin t\cos t}+\dfrac{2\sin t\cos t}{\sin t\cos t}$ and simplify: $\dfrac{1}{\sin t\cos t}+\dfrac{2\sin t\cos t}{\sin t\cos t}=2+\sec t\csc t$ $\dfrac{1}{\sin t\cos t}+2=2+\sec t\csc t$ On the left side, $\dfrac{1}{\sin t\cos t}$ can be rewritten as $\Big(\dfrac{1}{\sin t}\Big)\Big(\dfrac{1}{\cos t}\Big)$: $2+\Big(\dfrac{1}{\sin t}\Big)\Big(\dfrac{1}{\cos t}\Big)=2+\sec t\cos t$ Since $\dfrac{1}{\sin t}=\csc t$ and $\dfrac{1}{\cos t}=\sec t$, the identity is proved: $2+\sec t\cos t=2+\sec t\cos t$
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