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 - Page 68: 79

Answer

The hole is located at $$(0,3)$$

Work Step by Step

So, the general function is $$f(x)=\frac{sin(3t)}{t}$$ With the graph, which can be seen down below, you can see and assume that there would be a hole at exactly $0,3$ since when you plug in $0$ into the original function, $0$ will be in the denominator by itself and anything divided by $0$ is undefined. So, we can create a table of the points to between $0$, from both the left and the right of $0$, to see what is happening on both sides, which can be written as the following: $$\begin{matrix} t & &f(t) \\ -0.1 & \frac{sin(3(-0.1))}{(-0.1)} &2.96 \\\\ -0.01 & \frac{sin(3(-0.01))}{(-0.01)} &2.9996 \\\\ -0.001 & \frac{sin(3(-0.001))}{(-0.001)} &3 \\\\ 0 & \frac{sin(3(0))}{(0)} &DNE \\\\ 0.001 & \frac{sin(3(0.001))}{(0.001)} &3 \\\\ 0.01 & \frac{sin(3(0.01))}{(0.01)} &2.9996 \\\\ 0.1 & \frac{sin(3(0.1))}{(0.1)} & 2.96 \end{matrix}$$ Based on this table, the limit is appearing to be at $3$ when $t$ is approaching $0$ despite it does not exist at exactly $0$. So, this graph does have an undefined point, or hole, when $(0,C(t))$ so to (properly and not assume) figure out the $y$-value you would have to find the limit of the function as $t$ is approaching $0$, which can be $t \rightarrow 0$, which can be written as the following: $$\begin{matrix} \lim _{t\to 0}\left(\frac{\sin \left(3t\right)}{t}\right)&=\lim _{t\to 0}\left(\frac{f'(\sin \left(3t\right))}{f'(t)}\right)\\ &=\lim _{t\to 0}\left(\frac{f'(3t)\cos \left(3t\right)}{1}\right)\\ &=\lim _{t\to 0}\left(\frac{3\cos \left(3t\right)}{1}\right)\\ &=\lim _{t\to 0}3\cos \left(3t\right)\\ &=3\cos \left(3(0)\right)\\ &=3\cos \left(0\right)\\ &=3\left(1\right)\\ C(t)&=\mathbf{3}\\ \end{matrix}$$ Since $C(t)=3$, then this means that the hole is exactly at $$(0,3)$$
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