# Year 9

## Measurement and Geometry

### Trigonometry

The study of angles and of the angular relationships of planar and three-dimensional figures is known as trigonometry. The Babylonians, Chinese, Egyptians (using a merkhet) and Hindu cultures all had devices for measuring altitude and lateral displacement of heavenly bodies. Although trigonometry was originally developed to solve problems related to astronomy, it soon found applications to navigation and a wide range of other areas. It is of great practical importance to builders, architects and surveyors.

We initially restrict our attention to right-angled triangles.

Illustration © Nives Porcellato and Andrew Craig