6.5. Transformations exercises#
Answer the following exercises based on the content from this chapter. The solutions can be found in the appendices.
Which of the following transformations are linear transformations?
(a) \(T: (x, y)^\mathsf{T} \mapsto (0, y)^\mathsf{T}\)
(b) \(T: (x, y)^\mathsf{T} \mapsto (x, 5)^\mathsf{T}\)
(c) \(T: (x, y, z)^\mathsf{T} \mapsto (x, x - y)^\mathsf{T}\)
(d) \(T: (x, y, z)^\mathsf{T} \mapsto \begin{pmatrix} x + y \\ z \end{pmatrix}\)
(e) \(T: (x, y)^\mathsf{T} \mapsto (3x + 1, y)^\mathsf{T}\)
(f) \(T: f(x) \mapsto \dfrac{\mathrm{d}}{\mathrm{d}x} f(x)\)
(g) \(T: f(x) \mapsto xf(x)\)
(h) \(T: \mathbb{C}^2 \to \mathbb{C}\) where \(T: (x, y)^\mathsf{T} \mapsto x + y\)
(i) \(T: \mathbb{C}^2 \to \mathbb{C}\) where \(T: (x, y)^\mathsf{T} \mapsto x y\)
(j) \(T: \mathbb{C}^2 \to \mathbb{C}\) where \(T: (x, y)^\mathsf{T} \mapsto \bar{y}\)
(\(\bar{x}\) is the complex conjugate of \(x = a + bi\) defined by \(\bar{x} = a - bi\).)
A linear transformation \(T: \mathbb{R}^2 \to \mathbb{R}^2\) is defined by \(T: (x, y)^\mathsf{T} \mapsto (-x + 3y, x - 4y)^\mathsf{T}\). Determine the transformation matrix for \(T\) and hence calculate \(T (2, 5)^\mathsf{T}\).
A linear transformation \(T: \mathbb{R}^2 \to \mathbb{R}^2\) is defined by \(T: (x, y)^\mathsf{T} \mapsto (x - 2y, 2x + 3y)^\mathsf{T}\). Given \(T(\vec{u}) = (-1, 5)^\mathsf{T}\) determine \(\vec{u}\).
\(T: \mathbb{R}^3 \to \mathbb{R}^3\) is a linear transformation such that
Find the transformation matrix for \(T\).
Rotate the position vector \((2, 1)^\mathsf{T} \in \mathbb{R}^2\) by angle \(\pi/6\) anti-clockwise about the origin.
Reflect the position vector \((5, 3)^\mathsf{T} \in \mathbb{R}^2\) about the line that passes through \((0, 0)\) and makes an angle \(\pi/3\) with the \(x\)-axis.
A square with side lengths 2 is centred at the co-ordinates \((3, 2)\). It is to be translated so the centre is at the origin, rotated by an angle \(\pi/3\) clockwise about the origin and then translated back to its initial position.
(a) Write down a matrix containing the homogeneous co-ordinates for the vertices of the square.
(b) Determine the transformation matrices that perform the three transformations.
(c) Calculate the composite transformation matrix and apply with to the co-ordinate matrix from part (a).