 # Trigonometric Identities

Note by , created almost 6 years ago

## This note gives a list of some useful formulae for solving equations involving trigonometric functions 185 4 0  Created by rory.examtime almost 6 years ago
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Trigonometric identities are formulae that exist between the trigonometric functions.

They are useful for solving algebraic problems involving trigonometric functions.

Here is a list of some common trigonometric identities:

﻿﻿Sin^2(A) + Cos^2(A) = 1

﻿﻿﻿       1       ﻿ = tan^2(A) + 1Cos^2(A)

﻿Sin(2A) = 2Sin(A)Cos(A) ﻿﻿

﻿﻿Cos(2A) = Cos^2(A) - Sin^2(A)

﻿﻿tan(2A) = ﻿    2tan(A)    ﻿                 1 - tan^2(A)

﻿﻿Sin(A+B) = Sin(A)Cos(B) + Cos(A)Sin(B)

﻿﻿Sin(A-B) = Sin(A)Cos(B) - Cos(A)Sin(B)

﻿﻿Cos(A+B) = Cos(A)Cos(B) - Sin(A)Sin(B)

﻿﻿Cos(A-B) = Cos(A)Cos(B) + Sin(A)Sin(B)

﻿tan(A+B) = ﻿   tan(A) + tan(B)   ﻿                      1 - tan(A)tan(B)

﻿﻿tan(A-B) = ﻿  tan(A) - tan(B)  ﻿                   1 + tan(A)tan(B)

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