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MATH3061 Geometry and Topology Geometry Assignment
All solutions need to be justified.
The assignment must be submitted electronically as a single PDF file using Turnitin in Canvas.
You may submit scanned copies of handwritten solutions or typeset your work. Note that
your assignment will not be marked if it is illegible or poorly scanned or submitted sideways
or upside down. It is your responsibility to check that your assignment has been submitted
correctly.
Question 1. Let α : E → E be defined by α(x, y) = (3x− 1, x+ 2y + 1).
(a) Prove that α is a transformation.
(b) Let ℓ be the line given by the equation 2x + y − 1 = 0. Find the Cartesian equation of
α(ℓ).
(c) Is α an involution or isometry?
Question 2. Let Q = (2, 3) and v =
[
3
2
]
.
(a) Find the Cartesian equation of the line ℓ through Q in direction v.
(b) Find the Cartesian equation of the line m such that ρQ,π/2 = σℓσm.
(c) What is the isometry σ−1m ◦ ρQ,π/2 ◦ σm?
Question 3. Denote by a, b the lines with the Cartesian equations y = 1, x = −1 respectively,
and i =
[
1
0
]
, j =
[
0
1
]
.
(a) Find the functions f(x, y) and g(x, y) such that γb,j(x, y) = (f(x, y), g(x, y)).
(b) Find the equation of the line γb,j(a).
(c) What is the isometry γb,jγa,i?
Question 4. Let A, B be two distinct points in the plane. Denote by G the set of all isometries
which map the set {A,B} to itself.
(a) Describe all isometries of G. (Your answer should consist of a list specifying the reflections,
rotations, translations and/or glide-reflections which belong to G.)
(b) Is G a group?
(c) Find all subsets of G which are groups.