Dot product
A single number obtained by multiplying matching components of two vectors and adding the results.
For vectors a and b, the dot product a · b = Σ aᵢ bᵢ equals |a||b|cos θ, where θ is the angle between them. It is zero exactly when the vectors are perpendicular and is the cornerstone of orthogonality in linear algebra.
Formula
a · b = Σ aᵢ bᵢ = |a||b| cos θ