Non-Right-Angled Triangles (AQA AS Maths): Revision Note
Did this video help you?
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
![Non-Right-Angled Triangles Diagram 1a, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.1.3-Non-Right-Angled-Triangles-Diagram-1a.png)
![Non-Right-Angled Triangles Diagram 1b, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.1.3-Non-Right-Angled-Triangles-Diagram-1b.png)
![Non-Right-Angled Triangles Diagram 1c, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.1.3-Non-Right-Angled-Triangles-Diagram-1c.png)
![Non-Right-Angled Triangles Diagram 1d, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.1.3-Non-Right-Angled-Triangles-Diagram-1d.png)
How do I know which rule to use?
![Non-Right-Angled Triangles Diagram 2, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.1.3-Non-Right-Angled-Triangles-Diagram-2.png)
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
![Non-Right-Angled Triangles Example Diagram, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.1.3-Non-Right-Angled-Triangles-Example-Diagram.png)
![Non-Right-Angled Triangles Example Solution, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.1.3-Non-Right-Angled-Triangles-Example-Solution.png)
You've read 0 of your 5 free revision notes this week
Sign up now. It’s free!
Did this page help you?