Angle Between Two Vectors (Dot Product) (cos θ = (a·b)/(|a||b|))

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cos θ = (a·b)/(|a||b|)

What each symbol means

SymbolWhat it stands for
\thetaAngle between directions of a and b
0 ≤ θ ≤ πPrincipal angle in vector sense

When to use this

Non-zero vectors. For zero vector, angle undefined.