Half-Angle Tangent (half-angle tangent)

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half-angle tangent

What each symbol means

SymbolWhat it stands for
A,B,COpposite angles
a,b,cSide lengths
R,r,s,ΔCircumradius, inradius, semiperimeter, area

When to use this

Valid for Euclidean triangle with positive sides satisfying triangle inequality.