VECTOR
by Robyn Arianrhod (UNSW Press, $49.99)
Imagine an arrow on a computer screen –in PowerPoint, say. You can drag it around the screen and it’s the same arrow. You can make different arrows by stretching it or rotating it to point in a different direction. Each of these arrows can be described by two numbers: horizontal and vertical distance, or angle and length, or in many other equivalent ways.