Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 1 - Limits and Their Properties - 1.3 Exercises: 74

Answer

$\lim\limits_{x\to0}\dfrac{\sin{2x}}{\sin{3x}}=\dfrac{2}{3}.$

Work Step by Step

Using Theorem $1.9:$ $\lim\limits_{x\to0}\dfrac{\sin{2x}}{\sin{3x}}=\lim\limits_{x\to0}\dfrac{2\sin{2x}}{2x}\times\lim\limits_{x\to0}\dfrac{3x}{3\sin{3x}} =\frac{2}{3}\lim\limits_{x\to0}\dfrac{\sin{2x}}{2x}\times\lim\limits_{x\to0}\dfrac{3x}{\sin{3x}}$ Let $y=2x$ and $z=3x$. Note that as $x\to0$, so does $y\to0$ and $z\to0$. $=\frac{2}{3}\lim\limits_{y\to0}\dfrac{\sin{y}}{y}\times\lim\limits_{z\to0}\dfrac{z}{\sin{z}}=(\frac{2}{3})(1)(1)=\dfrac{2}{3}.$
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