Edexcel A Level Maths: Pure

Revision Notes

5.3.1 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

 

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

 

 

Trigonometry - Simple Identities Diagram 2b, A Level & AS Level Pure Maths Revision Notes

 

How to use the identities

Trigonometry - Simple Identities Diagram 3, A Level & AS Level Pure Maths Revision Notes

Exam Tip

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

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