Chapter 11: Problem 1
What is the derivative of \(\mathbf{r}(t)=\langle f(t), g(t), h(t)\rangle ?\)
Chapter 11: Problem 1
What is the derivative of \(\mathbf{r}(t)=\langle f(t), g(t), h(t)\rangle ?\)
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Get started for freeHexagonal circle packing The German mathematician Gauss proved that the densest way to pack circles with the same radius in the plane is to place the centers of the circles on a hexagonal grid (see figure). Some molecular structures use this packing or its three-dimensional analog. Assume all circles have a radius of 1 and let \(\mathbf{r}_{i j}\) be the vector that extends from the center of circle \(i\) to the center of circle \(j,\) for \(i, j=0,1, \ldots, 6\) a. Find \(\mathbf{r}_{0 j},\) for \(j=1,2, \ldots, 6\) b. Find \(\mathbf{r}_{12}, \mathbf{r}_{34},\) and \(\mathbf{r}_{61}\) c. Imagine circle 7 is added to the arrangement as shown in the figure. Find \(\mathbf{r}_{07}, \mathbf{r}_{17}, \mathbf{r}_{47},\) and \(\mathbf{r}_{75}\)
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 \(|\mathbf{u}+\mathbf{v}|=|\mathbf{u}|+|\mathbf{v}| ?\)
Let \(\mathbf{u}(t)=\left\langle 1, t, t^{2}\right\rangle, \mathbf{v}(t)=\left\langle t^{2},-2 t, 1\right\rangle\) and \(g(t)=2 \sqrt{t}\). Compute the derivatives of the following functions. $$\mathbf{v}\left(e^{t}\right)$$
Find the function \(\mathbf{r}\) that satisfies the given conditions. $$\mathbf{r}^{\prime}(t)=\frac{t}{t^{2}+1} \mathbf{i}+t e^{-t^{2}} \mathbf{j}-\frac{2 t}{\sqrt{t^{2}+4}} \mathbf{k} ; \mathbf{r}(0)=\mathbf{i}+\frac{3}{2} \mathbf{j}-3 \mathbf{k}$$
Compute the following derivatives. $$\frac{d}{d t}\left(t^{2}(\mathbf{i}+2 \mathbf{j}-2 t \mathbf{k}) \cdot\left(e^{t} \mathbf{i}+2 e^{t} \mathbf{j}-3 e^{-t} \mathbf{k}\right)\right)$$
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