Right-Angled Triangles (Cambridge (CIE) AS Maths) : Revision Note
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Right-Angled Triangles
What is SOHCAHTOA?
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?
Examiner Tips and Tricks
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
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