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:
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
How to use the identities
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.