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Half Angle Identities

Half Angle Identities
Half Number Identities

Trig identities that show how to find the sine, cosine, or tangent of half a given angle.

 

Half Angle Identities

Half angle identity formula: sin(x/2) = ±√((1 − cos x)/2)  or  Formula: sin²x = (1 − cos 2x) / 2, a half angle identity for sine squared.

cos(x/2) = ±√((1 + cos x) / 2)  or  cos²x = (1 + cos 2x) / 2, a half angle identity for cosine squared

tan(x/2) = ± sqrt((1 − cos x) / (1 + cos x))  or  Math formula: sin(x) divided by (1 + cos x)  or  (1 - cos x) / sin x

 

See also

Double angle identities