Trigonometric Identities

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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) + 1

Cos^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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