Chapter 11: Problem 6
Explain how to add two vectors geometrically.
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Chapter 11: Problem 6
Explain how to add two vectors geometrically.
These are the key concepts you need to understand to accurately answer the question.
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Hexagonal 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 \(\mathbf{r}_{75}\)
Consider the curve \(\mathbf{r}(t)=(a \cos t+b \sin t) \mathbf{i}+(c \cos t+d \sin t) \mathbf{j}+(e \cos t+f \sin t) \mathbf{k}\) where \(a, b, c, d, e,\) and \(f\) are real numbers. It can be shown that this curve lies in a plane. Graph the following curve and describe it. $$\begin{aligned}\mathbf{r}(t)=&\left(\frac{1}{\sqrt{2}} \cos t+\frac{1}{\sqrt{3}} \sin t\right) \mathbf{i}+\left(-\frac{1}{\sqrt{2}} \cos t+\frac{1}{\sqrt{3}} \sin t\right) \mathbf{j} \\\&+\left(\frac{1}{\sqrt{3}} \sin t\right) \mathbf{k} \end{aligned}$$
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. $$g(t) \mathbf{v}(t)$$
Evaluate the following definite integrals. $$\int_{0}^{\ln 2}\left(e^{-t} \mathbf{i}+2 e^{2 t} \mathbf{j}-4 e^{t} \mathbf{k}\right) d t$$
Graph the curve \(\mathbf{r}(t)=\left\langle\frac{1}{2} \sin 2 t, \frac{1}{2}(1-\cos 2 t), \cos t\right\rangle\) and prove that it lies on the surface of a sphere centered at the origin.
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