Mathematics Specification B - 4MB1 PearsonEdexcel

Matrix Transformations

Overview

Every 2 by 2 matrix secretly describes a way of moving every point in the plane at once: multiply a point's coordinates by the matrix and out comes its image after a reflection, a rotation, an enlargement, or a shear. Recognising which matrix produces which transformation, and combining several transformations into a single matrix, turns geometry into pure algebra.

This topic builds directly on matrix multiplication: you will meet the standard matrices for reflections in the coordinate axes and the lines y = x and y = -x, rotations about the origin, enlargements centred at the origin, and shears, then combine transformations by multiplying their matrices together.

Objectives

  1. Understand transformations of the plane associated with 2 x 2 matrices, including reflections, rotations about the origin and enlargements with centre at the origin
  2. Find and use combination of transformations using matrix multiplication

Lesson Note

Any point \((x, y)\) can be written as a column vector \(\begin{pmatrix} x \\ y \end{pmatrix}\). Multiplying this column vector by a 2 by 2 matrix produces a new column vector: the coordinates of the image point after a transformation. Every 2 by 2 matrix defines a transformation of the whole plane in exactly this way, and every transformation that can be described by a 2 by 2 matrix leaves the origin fixed, since multiplying the zero vector by any matrix always gives the zero vector back.

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Lesson Evaluation

Congratulations on completing the lesson on Matrix Transformations. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

  1. Which matrix represents a reflection in the y-axis? A) [[1,0],[0,-1]] B) [[-1,0],[0,1]] C) [[0,1],[1,0]] D) [[-1,0],[0,-1]] Answer: B
  2. Which matrix represents a 90 degree anticlockwise rotation about the origin? A) [[0,1],[-1,0]] B) [[0,-1],[1,0]] C) [[-1,0],[0,-1]] D) [[1,0],[0,1]] Answer: B
  3. The matrix [[4,0],[0,4]] represents: A) a rotation of 90 degrees B) a reflection in the x-axis C) an enlargement, scale factor 4, centre the origin D) a shear Answer: C
  4. If R is carried out first, followed by M, the matrix for the combined transformation is: A) RM B) MR C) R + M D) M - R Answer: B
  5. A matrix that represents a shear parallel to the x-axis has the form: A) [[1,0],[k,1]] B) [[1,k],[0,1]] C) [[k,0],[0,k]] D) [[0,1],[1,0]] Answer: B

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Available on the Green Bridge App

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