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Use a rotation matrix to rotate the vector \(\left[\begin{array}{l}-2 \\\ -3\end{array}\right]\) counterclockwise by the angle \(\pi / 2\).

Short Answer

Expert verified
The rotated vector is \( \begin{bmatrix} 3 \\ -2 \end{bmatrix} \).

Step by step solution

01

Understanding the Rotation Matrix

To rotate a vector counterclockwise in 2D, we use a rotation matrix. The rotation matrix for an angle \( \theta \) is given by: \[R(\theta) = \begin{bmatrix} \cos(\theta) & -\sin(\theta) \ \sin(\theta) & \cos(\theta) \end{bmatrix}\]In this problem, \( \theta = \pi/2 \). Substitute this into the matrix.
02

Substituting the Angle

Substitute \( \theta = \pi/2 \) into the rotation matrix:\[R(\pi/2) = \begin{bmatrix} \cos(\pi/2) & -\sin(\pi/2) \ \sin(\pi/2) & \cos(\pi/2) \end{bmatrix} = \begin{bmatrix} 0 & -1 \ 1 & 0 \end{bmatrix}\]
03

Performing the Matrix Multiplication

To rotate the vector \( \begin{bmatrix} -2 \ -3 \end{bmatrix} \), multiply the rotation matrix by this vector:\[\begin{bmatrix} 0 & -1 \ 1 & 0 \end{bmatrix} \begin{bmatrix} -2 \ -3 \end{bmatrix} = \begin{bmatrix} (0)(-2) + (-1)(-3) \ (1)(-2) + (0)(-3) \end{bmatrix}\]
04

Calculating the Result

Perform the calculations:\[\begin{bmatrix} (0)(-2) + (-1)(-3) \ (1)(-2) + (0)(-3) \end{bmatrix} = \begin{bmatrix} 0 + 3 \ -2 + 0 \end{bmatrix} = \begin{bmatrix} 3 \ -2 \end{bmatrix}\]
05

Interpreting the Result

The rotated vector is \( \begin{bmatrix} 3 \ -2 \end{bmatrix} \). This means after rotating \( \begin{bmatrix} -2 \ -3 \end{bmatrix} \) by \( \pi/2 \) counterclockwise, the new position of the vector is \( \begin{bmatrix} 3 \ -2 \end{bmatrix} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Vector Rotation
When we talk about vector rotation, we are dealing with turning or rotating a vector around a specific point, usually the origin, without altering its magnitude. Imagine holding a stick at one end and spinning it around in a circle — its length doesn't change, just the direction it points in. In math terms, we use something called a rotation matrix to achieve this.

The rotation matrix is a special grid or table of numbers that, when multiplied by a vector, gives us the rotated version of that vector. It is essential in 2D space for transforming whether you wish to rotate an object on a plane by some angle \( \theta \). This process is crucial in various applications, ranging from graphics in video games to robot path planning. By using the rotation matrix, we can rotate a vector without changing its size or length, only its direction.

Key points to remember about vector rotation include:
  • It doesn't alter the vector's magnitude but changes its direction.
  • The rotation can be either clockwise or counterclockwise.
  • The origin is often the pivot point for rotation.
Trigonometry
Trigonometry might sound like a scary term, but it is all about the relationships between the angles and lengths of triangles. In vector rotation, we use trigonometric functions like sine and cosine to help describe and compute how much a vector should turn in either direction.

The rotation matrix, which we use to rotate vectors, relies on these trigonometric functions. For an angle \( \theta \), the basic structure of a rotation matrix is:\[ R(\theta) = \begin{bmatrix} \cos(\theta) & -\sin(\theta) \sin(\theta) & \cos(\theta) \end{bmatrix} \]
Here's how trigonometry plays a crucial role:
  • \(\cos(\theta)\) gives us how much of the vector remains in its original direction after the rotation.
  • \(-\sin(\theta)\) and \(\sin(\theta)\) indicate how the vector shifts vertically and horizontally, respectively.
  • As angles change, so do the projections of the vector onto different axes, all thanks to sine and cosine.

Trigonometry thus acts as the bridge between the angular shifts we want and the numerical operations needed to achieve them.
Linear Algebra
Linear algebra forms the backbone of operations involving matrices and vectors, which are key players in many advanced mathematical techniques. When we engage in vector rotations, we utilize linear algebra's machinery to manage and manipulate data in structured ways through matrices and vectors.

You can think of a matrix like a tool that reshapes or moves a vector, much like using a spanner to tighten a bolt. In our context, the rotation matrix is a specific kind of matrix that directs how a vector should twist and turn on a plane. Here are important aspects of linear algebra in this process:
  • Matrix multiplication allows us to apply the rotation to the vector systematically.
  • Vectors are like arrows in space, defined by their direction and magnitude — key entities we manipulate using matrices.
  • The resulting vector from matrix multiplication reveals the new position of our rotated vector.

Through the lens of linear algebra, these operations become not just geometrical intuitions, but precise calculations that we can rely on in varied fields ranging from computer graphics to physics simulations.

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Most popular questions from this chapter

Assume that a population is divided into three age classes and that \(80 \%\) of the females age 0 and \(10 \%\) of the females age present at time \(t\) survive until time \(t+1\). Assume further that females age 1 have an average of \(1.6\) female offspring and females age 2 have an average of \(3.9\) female offspring. If, at time 0 , the population consists of 1000 females age 0,100 females age 1 , and 20 females age 2 , find the Leslie matrix and the number of females in each age class at time \(3 .\)

Suppose that $$ L=\left[\begin{array}{ll} 3 & 2 \\ 1.5 & 1 \end{array}\right] $$ is the Leslie matrix for a population with two age classes. (a) Determine both eigenvalues. (b) Give a biological interpretation of the larger eigenvalue. (c) Find the stable age distribution.

Find the equation of the plane through \((1,-1,2)\) and perpendicular to \([-1,1,2]^{\prime}\).

Find the eigenvalues \(\lambda_{1}\) and \(\lambda_{2}\) and corresponding eigenvectors \(\mathrm{v}_{1}\) and \(\mathrm{v}_{2}\) for each matrix A. Determine the equations of the lines through the origin in the direction of the eigenvectors \(\mathrm{v}_{1}\) and \(\mathrm{v}_{2}\), and graph the lines together with the eigenvectors \(\mathrm{v}_{1}\) and \(\mathrm{v}_{2}\) and the vectors \(\mathrm{Av}_{1}\) and \(\mathrm{Av}_{2}\) $$A=\left[\begin{array}{ll}-2 & -1 \\ -2 & -1\end{array}\right]$$

Find the parametric equation of the line in the \(x-y\) plane that goes through the given points. Then eliminate the parameter to find the equation of the line in standard form. \((2,3)\) and \((-1,-4)\)

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