Chapter 1 word hunt

Word hunt: Orienting Yourself: The Use of Coordinates

12 key words from this chapter are hidden in the grid. Find each one to unlock a short explanation. Your grid and the words you have found are remembered until you finish or ask for a new grid: on this device, or in your account on every device when you are signed in.

Origin: The point (0, 0) where the x-axis and the y-axis cross. Every position on the plane is measured from here.

Axis (plural: axes): One of the two number lines of the coordinate plane. The flat one going left and right is the x-axis. The upright one going up and down is the y-axis.

Quadrant: One of the four parts the axes cut the plane into, numbered I to IV going anticlockwise from the top right. Their signs are I (+, +), II (−, +), III (−, −) and IV (+, −). Points on an axis are in no quadrant.

Coordinates: The pair of numbers (x, y) that gives a point's exact position, like an address. Read it in order: first across (x), then up or down (y).

Abscissa: Another name for the x-coordinate, the first number in (x, y). It tells you how far the point is to the right (+) or left (−) of the y-axis.

Ordinate: Another name for the y-coordinate, the second number in (x, y). It tells you how far the point is above (+) or below (−) the x-axis.

Cartesian plane: The flat surface with the two axes on it, named after René Descartes. It is also called the coordinate plane or the xy-plane.

Distance formula: The straight distance between (x₁, y₁) and (x₂, y₂) is √((x₂ − x₁)² + (y₂ − y₁)²). It comes from the Baudhāyana-Pythagoras theorem: walk across, walk up, then take the shortcut.

Midpoint: The point exactly halfway between two points. Average the two x-coordinates and average the two y-coordinates.

Reflection: A mirror image. Reflecting in the y-axis turns (x, y) into (−x, y). Reflecting in the x-axis turns (x, y) into (x, −y). All lengths stay the same.

Hypotenuse: The longest side of a right-angled triangle, opposite the right angle. The straight distance between two points is the hypotenuse of the right triangle made by walking across and then up.

Scale: How a length on a drawing compares with the real length. Shalini's map used 1 cm : 1 foot, so every centimetre on the board stood for one foot in the room.