Non-Right-Angled Triangles (Edexcel International AS Maths) : Revision Note
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Non-Right-Angled Triangles
What do I do if there isn’t a right‑angle?
The Sine Rule, Cosine Rule and Area Formula can be used for ANY type of triangle
They can help us calculate missing side lengths, angles and area
How do I know which rule to use?
Once you know which rule to use, simply label your triangle, substitute in the values and rearrange if necessary
Examiner Tips and Tricks
If you are given two angles in a triangle, finding the missing angle by subtracting from 180° might help.
Make sure you are careful to pick the correct rule to use, you’ll need to remember all the rules as they aren’t in the formula booklet.
Make sure your calculator is in degree mode (D).
Always check your answers are sensible…
Have I remembered to square root at the end?
Have I remembered to use -1?
Check if the question asks you to round your answer.
Worked Example
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