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Assessment for Unit 4: Functions Involving Parameters, Vectors, and Matrices
Select the one best answer for each question.
1. A curve is defined by the parametric equations $x(t) = t^2 - 2$ and $y(t) = t$ for the interval $-2 \le t \le 2$. Which of the following statements best describes the graph of the curve in the $xy$-plane?
2. The position of a particle at time $t$ is given by the parametric function $f(t) = (x(t), y(t))$, where $x(t) = 3\cos(t)$ and $y(t) = 3\sin(t)$ for $\pi \le t \le 2\pi$. Which of the following describes the path of the particle?
3. [Skill: 2A | Topic: 4.1] A parametric function in the plane is defined by the table of values below, where points are generated in order of increasing parameter value $t$. $t$: $-2, -1, 0, 1, 2$ $x(t)$: $4, 1, 0, 1, 4$ $y(t)$: $-2, -1, 0, 1, 2$ Which of the following best describes the graph that is traced by the parametric function as $t$ increases from $-2$ to $2$?
4. Consider the parametric function defined by $x(t) = \sqrt{t}$ and $y(t) = t - 1$ for $t \ge 0$. Which of the following best describes the graph of the function in the $xy$-plane?
5. Let $A$ be a matrix of dimension $2 \times 4$ and let $B$ be a matrix of dimension $4 \times 3$. Which of the following correctly describes the existence and dimensions of the matrix products $AB$ and $BA$?
6. Let $M = \begin{pmatrix} 2 & -3 \\ 4 & 1 \end{pmatrix}$ and $N = \begin{pmatrix} 5 & 0 \\ 2 & -1 \end{pmatrix}$. What is the product $MN$?
7. Matrices $A$ and $B$ are defined as follows: $$ A = \begin{pmatrix} 1 & 4 \\ -2 & 3 \\ 0 & 5 \end{pmatrix}, \quad B = \begin{pmatrix} 2 & -1 \\ 6 & 0 \end{pmatrix} $$ If $C = AB$, what is the value of the entry $c_{21}$ (the element in the second row and first column of $C$)?
8. Let $A = \begin{pmatrix} 3 & k \\ 1 & 2 \end{pmatrix}$ and $X = \begin{pmatrix} 2 \\ -1 \end{pmatrix}$. If the product $AX = \begin{pmatrix} 1 \\ 0 \end{pmatrix}$, what is the value of the parameter $k$?
9. Let $A$ be the matrix defined by $A = \begin{pmatrix} 4 & 2 \\ -3 & -1 \end{pmatrix}$. Which of the following represents $A^{-1}$?
10. For what value of constant $k$ does the matrix $M = \begin{pmatrix} 6 & k \\ -2 & 5 \end{pmatrix}$ not have an inverse?
11. Matrices $A$ and $B$ are inverses of each other. If $A = \begin{pmatrix} 3 & 1 \\ 4 & 2 \end{pmatrix}$ and $B = \begin{pmatrix} 1 & -0.5 \\ x & 1.5 \end{pmatrix}$, what is the value of $x$?
12. Which of the following matrices represents a linear transformation that maps distinct vectors to the same vector (is not one-to-one), and why?
13. A linear transformation $L: \mathbb{R}^2 \to \mathbb{R}^2$ is defined by the matrix $A = \begin{pmatrix} 2 & -3 \\ 1 & 4 \end{pmatrix}$, such that $L(\vec{v}) = A\vec{v}$. Which of the following vectors is the image of the input vector $\vec{v} = \langle 5, 2 \rangle$ under this transformation?
14. The linear transformation $T$ maps a vector $\vec{u} = \langle x, y \rangle$ to a vector $\vec{w}$ using the rule $T(\vec{u}) = \begin{pmatrix} 0 & -1 \\ 1 & 0 \end{pmatrix} \begin{pmatrix} x \\ y \end{pmatrix}$. If a triangle has vertices at points $(2, 0)$, $(4, 1)$, and $(2, 3)$, which of the following gives the coordinates of the vertices of the transformed triangle?
15. A linear transformation maps input vectors to output vectors according to the equations $x' = 3x + 2y$ and $y' = -x + 5y$, where $\langle x, y \rangle$ is the input vector and $\langle x', y' \rangle$ is the output vector. If the input vectors are represented by the matrix $B = \begin{pmatrix} 1 & 0 \\ -2 & 4 \end{pmatrix}$, where each column is a vector, which matrix represents the corresponding output vectors?
16. The linear transformation $L: \mathbb{R}^2 \to \mathbb{R}^2$ rotates every vector counterclockwise by an angle of $\theta = \frac{2\pi}{3}$ radians about the origin. Which of the following matrices is associated with the transformation $L$?
17. Let $f$ and $g$ be linear transformations defined by $f(\vec{v}) = A\vec{v}$ and $g(\vec{v}) = B\vec{v}$, where $A = \begin{pmatrix} 2 & 1 \\ 0 & -1 \end{pmatrix}$ and $B = \begin{pmatrix} 3 & 0 \\ 1 & 2 \end{pmatrix}$. Which of the following matrices represents the composite transformation $h(\vec{v}) = f(g(\vec{v}))$?
18. A linear transformation $T$ is represented by the matrix $M = \begin{pmatrix} -2 & 4 \\ 3 & 1 \end{pmatrix}$. If a region $R$ in the $xy$-plane has an area of 5 square units, what is the area of the image of $R$ under the transformation $T$?
19. A logistics company manages a fleet of delivery trucks that operate between two main distribution centers, Center A and Center B. Each morning, the trucks are dispatched from their current location. Historical data indicates the following transition probabilities for the trucks' locations by the end of the day: - Of the trucks starting at Center A, 70% return to Center A and 30% end up at Center B. - Of the trucks starting at Center B, 45% end up at Center A and 55% return to Center B. Let $V_t = \begin{bmatrix} a_t \\ b_t \end{bmatrix}$ represent the number of trucks at Center A and Center B, respectively, on day $t$. Which of the following matrix equations correctly models the distribution of trucks on day $t+1$ based on the distribution on day $t$?
20. A simplified weather model for a specific region classifies each day as either Sunny (S) or Rainy (R). The transition between these states from one day to the next is modeled by the matrix equation $W_{n+1} = T W_n$, where $W_n = \begin{bmatrix} S_n \\ R_n \end{bmatrix}$ and $T = \begin{bmatrix} 0.8 & 0.4 \\ 0.2 & 0.6 \end{bmatrix}$. If the weather on Day 0 is represented by the initial state vector $W_0 = \begin{bmatrix} 100 \\ 0 \end{bmatrix}$ (indicating a 100% certainty of a Sunny day), what is the state vector $W_2$ representing the probabilities for the weather on Day 2?
21. A biology student uses a matrix model to track the movement of a beetle population between two distinct zones in a terrarium. The population distribution at hour $k$ is given by the vector $P_k$, and the distribution at the next hour is given by $P_{k+1} = M P_k$, where $M$ is an invertible matrix. If the student observes the population distribution at hour 10 ($P_{10}$), which of the following expressions correctly represents the population distribution at hour 8 ($P_8$)?
22. A particle moves in the $xy$-plane such that its position $(x(t), y(t))$ for time $t > -5$ is given by the parametric equations $x(t) = t^2 - 2t - 8$ and $y(t) = \ln(t + 5)$. At which points does the path of the particle intersect the $y$-axis?
23. The position of an object moving in a plane is defined by the parametric functions $x(t) = 5 - 3\sin(2t)$ and $y(t) = 4 + \cos(2t)$. What is the domain of the curve traced by the object (the set of all possible $x$-coordinates)?
24. A parametric function is defined by $x(t) = 2t + 4$ and $y(t) = t^2 - 1$ for all real numbers $t$. Which of the following Cartesian equations represents the graph of this function?
25. [Skill: 2.B | Topic: 4.3] The table below gives values for the parametric functions $x(t)$ and $y(t)$ at selected values of time $t$. | $t$ | $x(t)$ | $y(t)$ | |:---:|:---:|:---:| | 0 | 1 | 2 | | 1 | 3 | 6 | | 2 | 6 | 9 | | 3 | 10 | 11 | Based on the values in the table, which of the following best describes the motion of the particle for $0 \le t \le 3$?
26. [Skill: 1.C | Topic: 4.3] A particle moves in the $xy$-plane such that its position for $t \ge 0$ is given by the parametric equations $x(t) = t^2 + 1$ and $y(t) = 3t - 4$. What is the slope of the line segment connecting the point on the curve at $t=1$ to the point on the curve at $t=3$?
27. [Skill: 3.B | Topic: 4.3] The position of a particle moving in the $xy$-plane is defined by the parametric functions $x(t) = \sqrt{t}$ and $y(t) = 2t - 3$ for $t \ge 0$. Which of the following Cartesian equations describes the path of the particle in the $xy$-plane?
28. A particle moves in the $xy$-plane along a linear path from the point $P(-2, 5)$ to the point $Q(4, -3)$ over the time interval $0 \le t \le 2$. Which of the following systems of parametric equations represents the position of the particle $(x(t), y(t))$ ?
29. A circle in the $xy$-plane has a radius of 3 and is centered at the point $(2, -1)$. A particle moves around this circle such that at time $t=0$, the particle is located at $(2, 2)$. The particle moves in a clockwise direction with a period of $2\pi$. Which of the following parametric systems could describe the motion of the particle?
30. A particle moves along the circle defined by $x^2 + y^2 = 16$. The particle starts at the point $(4, 0)$ at time $t=0$ and moves counterclockwise, completing one full revolution every 5 seconds. Which of the following parametric equations describes the $x$-coordinate of the particle's position as a function of $t$ ?
31. A relation between $x$ and $y$ is defined by the equation $(y+2)^2 = x - 3$. Which of the following equations represents a function $y = h(x)$ defined implicitly by this relation such that the range of $h$ is $(-\infty, -2]$?
32. The equation $3x^2 + y^2 = 12$ defines a relation between $x$ and $y$. If $y = g(x)$ is a function defined implicitly by this relation such that $g(0) > 0$, what is the domain of $g$?
33. A conic section is defined by the equation $x = \frac{1}{8}(y-3)^2 - 2$. Which of the following correctly describes the direction in which the conic section opens and the coordinates of its vertex?
34. An ellipse is defined by the equation $\frac{(x-1)^2}{16} + \frac{(y+4)^2}{9} = 1$. Which of the following lists the coordinates of the vertices of the ellipse?
35. A hyperbola has its center at $(2, -1)$ and a vertical transverse axis. Which of the following could be an equation for this hyperbola?
36. A curve in the plane is defined by the equation $y = \frac{3}{x-1}$. Which of the following sets of parametric equations represents this curve?
37. An ellipse is defined by the equation $\frac{(x+3)^2}{4} + \frac{(y-2)^2}{25} = 1$. Which of the following pairs of parametric equations could describe the graph of the ellipse?
38. A particle moves along a curve defined by the parametric equations $x(t) = 4 \sec t + 1$ and $y(t) = 3 \tan t - 2$ for $t$ in the domain $[0, 2\pi)$ where $\cos t \neq 0$. Which of the following Cartesian equations represents the curve traced by the particle?
39. Let $\vec{u} = \langle 3, -2 \rangle$ and $\vec{v} = \langle -1, 5 \rangle$. What is the magnitude of the vector $\vec{w} = 2\vec{u} - \vec{v}$?
40. Which of the following represents the unit vector in the same direction as the vector $\vec{v} = \langle -5, 12 \rangle$?
41. Two vectors, $\vec{a}$ and $\vec{b}$, have magnitudes $|\vec{a}| = 6$ and $|\vec{b}| = 4$. If the angle between the two vectors is $\frac{2\pi}{3}$, what is the value of the dot product $\vec{a} \cdot \vec{b}$?
42. A particle moves in the $xy$-plane. For time $t \ge 0$, the horizontal position of the particle is given by $x(t) = 2t + 3$ and the vertical position is given by $y(t) = t^2$. Which of the following vector-valued functions $\vec{p}(t)$ represents the position of the particle?
43. The position of a robotic vehicle moving on a flat surface is defined by the vector-valued function $\vec{r}(t) = \langle 5t - 2, 12t + 1 \rangle$, where $t$ is measured in seconds and distance is measured in meters. What is the speed of the vehicle, in meters per second, at time $t = 3$?
44. A vector-valued function is given by $\vec{p}(t) = \langle t - 2, (t - 2)^2 + 1 \rangle$ for all real numbers $t$. Which of the following Cartesian equations describes the path traced by the particle in the $xy$-plane?
45. The relationship between two variables, $x$ and $y$, is defined by the equation $x^2 - y^2 = 9$. The graph of this relation passes through the point $(5, 4)$. Which of the following statements correctly describes the relationship between the changes in $x$ and $y$ for points on the graph that are very close to $(5, 4)$?
Answer all parts of each question. Answers must be in essay form. Outlines or lists alone are not acceptable.
Question 46:
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Question 49: