Trigonometry - Proving Identities
based on the Addition formula sin(A ± B) and cos (A ± B)
The following identities are very useful in solving certain types of trig. equation. Try and learn them. However, it is a good exercise to try and prove them. They are all very similar in the method of proof, so I would encourage you to look at one and try some of the others.
Proof of (1)
Proof of (2)
Proof of (3)
Proof of (4)
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