Chapter 11: Problem 35
Graph the curves described by the following functions, indicating the positive orientation. $$\mathbf{r}(t)=e^{-t / 20} \sin t \mathbf{i}+e^{-t / 20} \cos t \mathbf{j}+t \mathbf{k}, \text { for } 0 \leq t<\infty$$
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Chapter 11: Problem 35
Graph the curves described by the following functions, indicating the positive orientation. $$\mathbf{r}(t)=e^{-t / 20} \sin t \mathbf{i}+e^{-t / 20} \cos t \mathbf{j}+t \mathbf{k}, \text { for } 0 \leq t<\infty$$
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Suppose \(\mathbf{u}\) and \(\mathbf{v}\) are vectors in the plane. a. Use the Triangle Rule for adding vectors to explain why \(|\mathbf{u}+\mathbf{v}| \leq|\mathbf{u}|+|\mathbf{v}| .\) This result is known as the Triangle Inequality. b. Under what conditions is \(|\mathbf{u}+\mathbf{v}|=|\mathbf{u}|+|\mathbf{v}| ?\)
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Use vectors to show that the midpoint of the line segment joining \(P\left(x_{1}, y_{1}\right)\) and \(Q\left(x_{2}, y_{2}\right)\) is the point \(\left(\frac{x_{1}+x_{2}}{2}, \frac{y_{1}+y_{2}}{2}\right)\) (Hint: Let \(O\) be the origin and let \(M\) be the midpoint of \(P Q\). Draw a picture and show that $$\left.\overrightarrow{O M}=\overrightarrow{O P}+\frac{1}{2} \overrightarrow{P Q}=\overrightarrow{O P}+\frac{1}{2}(\overrightarrow{O Q}-\overrightarrow{O P}) \cdot\right)$$
Compute the following derivatives. $$\frac{d}{d t}\left(\left(t^{3} \mathbf{i}-2 t \mathbf{j}-2 \mathbf{k}\right) \times\left(t \mathbf{i}-t^{2} \mathbf{j}-t^{3} \mathbf{k}\right)\right)$$
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