AQA A Level Maths: Pure复习笔记5.1.1 Trigonometry - Definitions

Trigonometry - Definitions

What is trigonometry?

  • Trigonometry looks at the relationship between side lengths and angles of triangles
  • It comes from the Greek words trigonon meaning ‘triangle’ and metron meaning ‘measure’
  • The three trigonometric functions Sine, Cosine and Tangent come from ratios of side lengths in right angled triangles


What is the unit circle and how does it help with trigonometry?

  • The unit circle is a circle with radius 1 and centre (0, 0)
  • It can be used to calculate trig values as a co‑ordinate point (x, y) on the circle
  • (x, y) = (cos θ, sin θ), where θ is the angle measured anticlockwise from the positive x‑axis
  • It allows us to calculate sin, cos and tan for angles greater than 90°


Worked Example

5.1.1-Trigonometry-Definitions-Example-Question 5.1.1-Trigonometry-Definitions-Example-Solution