AQA A Level Maths: Pure复习笔记5.1.2 Right-Angled Triangles

Right-Angled Triangles


  • SOH, CAH, and TOA are an easy way to remember the three basic trigonometry ratios
  • They show the relationship between an angle and the different sides of a right-angled triangle which we can label Hypotenuse, Adjacent and Opposite
  • We use them to find missing angles and sides for right‑angled triangles
    • Hypotenuse is the longest side of a right-angled triangle
    • Adjacent is the side next to the angle you are working with (in between the angle and the right angle)
    • Opposite is the side opposite the angle you are working with


  •  We use the inverse trig functions to find missing angles


How do I use SOHCAHTOA?


Exam Tip

  • Remember SOHCAHTOA are only for calculating missing sides and angles for right‑angled triangles
    • For non-right‑angled triangles you will need to use the Sine or Cosine rules.
  • Make sure your calculator is in degree mode (D).
  • Always check your answers are sensible…
    • Should my answer be longer or shorter than the sides I have already i.e. is it the hypotenuse?
    • Is my angle sensible…
    • Have I remembered to use -1?
  • Check if the question asks you to round your answer.

Worked Example

5.1.2-Right-Angled-Triangles-Example-Question 5.1.2-Right-Angled-Triangles-Example-Solution