Given 7(t) = (et, et, vZet), for t > 0. a) Determine whether 7 (t) uses arc length as the parameter. %3| b) If not, re-parameterize 7 (t) with respect to arc length.

Calculus: Early Transcendentals
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Author:James Stewart
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Chapter1: Functions And Models
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### Problem Statement

Given the vector function \(\vec{r}(t) = \langle e^t, \, e^t, \, \sqrt{2}e^t \rangle\), for \(t \geq 0\):

a) Determine whether \(\vec{r}(t)\) uses arc length as the parameter.

b) If not, re-parameterize \(\vec{r}(t)\) with respect to arc length.

### Explanation and Solution Approach

**a) Determine whether \(\vec{r}(t)\) uses arc length as the parameter:**

To determine whether the given vector function \(\vec{r}(t)\) uses arc length \(s\) as the parameter, we need to check if the magnitude of the derivative of \(\vec{r}(t)\) with respect to \(t\) is 1 at all points. This means we need to calculate \(\left\|\frac{d\vec{r}}{dt}\right\|\).

Let's find \(\vec{r}'(t)\):

\[\vec{r}(t) = \langle e^t, \, e^t, \, \sqrt{2}e^t \rangle\]

\[\frac{d\vec{r}}{dt} = \langle \frac{d}{dt}(e^t), \, \frac{d}{dt}(e^t), \, \frac{d}{dt}(\sqrt{2}e^t) \rangle\]

\[\vec{r}'(t) = \langle e^t, \, e^t, \, \sqrt{2}e^t \rangle\]

Now, calculate the magnitude of \(\vec{r}'(t)\):

\[\left\|\vec{r}'(t)\right\| = \sqrt{(e^t)^2 + (e^t)^2 + (\sqrt{2}e^t)^2}\]

\[= \sqrt{e^{2t} + e^{2t} + 2e^{2t}}\]

\[= \sqrt{4e^{2t}}\]

\[= 2e^t\]

For \(\vec{r}(t)\) to use arc length as the parameter, \(\left\|\vec{r}'(
Transcribed Image Text:### Problem Statement Given the vector function \(\vec{r}(t) = \langle e^t, \, e^t, \, \sqrt{2}e^t \rangle\), for \(t \geq 0\): a) Determine whether \(\vec{r}(t)\) uses arc length as the parameter. b) If not, re-parameterize \(\vec{r}(t)\) with respect to arc length. ### Explanation and Solution Approach **a) Determine whether \(\vec{r}(t)\) uses arc length as the parameter:** To determine whether the given vector function \(\vec{r}(t)\) uses arc length \(s\) as the parameter, we need to check if the magnitude of the derivative of \(\vec{r}(t)\) with respect to \(t\) is 1 at all points. This means we need to calculate \(\left\|\frac{d\vec{r}}{dt}\right\|\). Let's find \(\vec{r}'(t)\): \[\vec{r}(t) = \langle e^t, \, e^t, \, \sqrt{2}e^t \rangle\] \[\frac{d\vec{r}}{dt} = \langle \frac{d}{dt}(e^t), \, \frac{d}{dt}(e^t), \, \frac{d}{dt}(\sqrt{2}e^t) \rangle\] \[\vec{r}'(t) = \langle e^t, \, e^t, \, \sqrt{2}e^t \rangle\] Now, calculate the magnitude of \(\vec{r}'(t)\): \[\left\|\vec{r}'(t)\right\| = \sqrt{(e^t)^2 + (e^t)^2 + (\sqrt{2}e^t)^2}\] \[= \sqrt{e^{2t} + e^{2t} + 2e^{2t}}\] \[= \sqrt{4e^{2t}}\] \[= 2e^t\] For \(\vec{r}(t)\) to use arc length as the parameter, \(\left\|\vec{r}'(
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