Simple Trigonometric Identities (Edexcel AS Maths): Revision Note
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Trigonometry - Simple Identities
What is a trigonometric identity?
Trigonometric identities are statements that are true for all values of x or theta (θ)
They are used to help simplify trig equations before solving them
The first two identities you must know are:
![Trigonometry - Simple Identities Diagram 1, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.3.1-Trigonometry-Simple-Identities-Diagram-1.png)
Where do these identities come from?
Although you don’t need to know the proof for these identities it is important to understand where they come from
![Trigonometry - Simple Identities Diagram 2a, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.3.1-Trigonometry-Simple-Identities-Diagram-2a.png)
![Trigonometry - Simple Identities Diagram 2b, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.3.1-Trigonometry-Simple-Identities-Diagram-2b.png)
How to use the identities
![Trigonometry - Simple Identities Diagram 3, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.3.1-Trigonometry-Simple-Identities-Diagram-3.png)
Examiner Tips and Tricks
You’ll need to remember these identities as they aren’t in the formula booklet.
If asked to show one thing is identical (≡) another look at what parts are missing – for example, if tan x has gone it must have been substituted.
Worked Example
![Trigonometry - Simple Identities Example Answer, A Level & AS Level Pure Maths Revision Notes](https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=3840/https://cdn.savemyexams.com/uploads/2020/06/5.3.1-Trigonometry-Simple-Identities-Example-Answer.png)
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