Chapter 11: Problem 72
Determine the values of \(x\) and \(y\) such that the points \((1,2,3),(4,7,1),\) and \((x, y, 2)\) are collinear (lie on a line).
Chapter 11: Problem 72
Determine the values of \(x\) and \(y\) such that the points \((1,2,3),(4,7,1),\) and \((x, y, 2)\) are collinear (lie on a line).
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Get started for freeA golfer launches a tee shot down a horizontal fairway; it follows a path given by \(\mathbf{r}(t)=\left\langle a t,(75-0.1 a) t,-5 t^{2}+80 t\right\rangle,\) where \(t \geq 0\) measures time in seconds and \(\mathbf{r}\) has units of feet. The \(y\) -axis points straight down the fairway and the \(z\) -axis points vertically upward. The parameter \(a\) is the slice factor that determines how much the shot deviates from a straight path down the fairway. a. With no slice \((a=0),\) sketch and describe the shot. How far does the ball travel horizontally (the distance between the point the ball leaves the ground and the point where it first strikes the ground)? b. With a slice \((a=0.2),\) sketch and describe the shot. How far does the ball travel horizontally? c. How far does the ball travel horizontally with \(a=2.5 ?\)
Explain why or why not Determine whether the following statements are true and
give an explanation or counterexample.
a. The vectors \(\mathbf{r}(t)\) and \(\mathbf{r}^{\prime}(t)\) are parallel for
all values of \(t\) in the domain.
b. The curve described by the function \(\mathbf{r}(t)=\left\langle t, t^{2}-2
t, \cos \pi t\right\rangle\)
is smooth, for \(-\infty
An ant walks due east at a constant speed of \(2 \mathrm{mi} / \mathrm{hr}\) on a sheet of paper that rests on a table. Suddenly, the sheet of paper starts moving southeast at \(\sqrt{2} \mathrm{mi} / \mathrm{hr} .\) Describe the motion of the ant relative to the table.
Use the formula in Exercise 79 to find the (least) distance between the given point \(Q\) and line \(\mathbf{r}\). $$Q(-5,2,9) ; \mathbf{r}(t)=\langle 5 t+7,2-t, 12 t+4\rangle$$
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 $$\left.\overrightarrow{O M}=\overrightarrow{O P}+\frac{1}{2} \overrightarrow{P Q}=\overrightarrow{O P}+\frac{1}{2}(\overrightarrow{O Q}-\overrightarrow{O P}) \cdot\right)$$
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