Geometric Bites

2×2 Orthogonal Matrix Mastery — A Generalised Construction Orthogonal matrices in two dimensions reveal one of the cleanest structures in linear algebra. A 2×2 matrix is orthogonal when its columns (and rows) satisfy two conditions: They are perpendicular (their dot product is zero); They have unit length (their magnitude is one). This article presents a clear generalisation: any pair of perpendicular vectors with equal magnitude can be normalised to form an orthogonal matrix. 1. Begin with two perpendicular vectors Let the first vector be: (a, b) A perpendicular vector can be chosen as: (−b, a) Their dot products confirm orthogonality: (a, b) · (−b, a) = −ab + ab = 0 (a, −b) · (b, a) = ab − ab = 0 2. Compute their shared magnitude Both vectors have the same length: |(a, b)| = √(a² + b²) We can therefore normalise each one by dividing by √(a² + b²). 3. Form the matrix using the normalised vectors Place the two normalised vectors...

What Is an Isometry? In geometry, some transformations distort shapes by stretching, squashing, or bending them. Others preserve the shape perfectly. These distortion-free transformations are called isometries . An isometry keeps every distance between points exactly the same. The object may move, rotate, or flip, but its size and structure remain unchanged. 1. The Core Idea A transformation f is an isometry if: distance( f(x), f(y) ) = distance( x, y ) for every pair of points x and y. This is the mathematical way of saying: nothing is stretched, compressed, or distorted. 2. A Simple Real-Life Analogy Place a phone on a desk. Slide it. Rotate it. Flip it. It remains the same phone—same size, same shape, same geometry. Each of those motions is an isometry . 3. What Isometries Never Do An isometry does not : stretch or shrink a shape, shear it diagonally, bend or curve it, change angles or proportions. It behaves exactly like movi...

Function Composition: A Simple Way to Organise Your Mathematics Function composition is one of the most useful tools in mathematics. It allows us to combine several steps into a single process, keeping our work neat, organised, and easy to reuse. Rather than performing one operation after another by hand, composition lets us build those steps into a single function. Once you become comfortable with function composition, you never want to go back to doing everything manually. It reduces clutter, helps you work systematically, and allows you to achieve remarkable results with only a few lines of equations. What Is Function Composition? A function takes an input, performs an operation, and produces an output. Function composition takes this idea further: it links functions together so that the output of one becomes the input of the next. We write this as: (f ∘ g)(x) = f(g(x)) This means that g acts first, then f . The circle symbol ∘ simply means “do one funct...

Common Transformations in Geometry: A Beginner’s Guide In geometry, a transformation is a rule that changes the position or appearance of a shape or a set of points. Some transformations simply move a shape to a new location, while others may turn it, resize it, or reflect it. Understanding these ideas helps us describe movement and change in a clear mathematical way. This guide introduces the most common transformations: translation, rotation, scaling, reflection, shear, and projection. Each section includes a simple example to make the ideas easier to follow. 1) Translation — Moving A translation shifts every point of a shape by the same amount. Nothing about the shape itself changes — not its size, not its proportions, and not its orientation. Only its position is different. Example: Imagine a triangle on graph paper. If every point of the triangle moves 3 units to the right and 2 units up, the triangle looks exactly the same — it simply appears somewhere else on th...