Dot (scalar) product
Three-dimensional geometry and vector algebra · Mathematics
Study notes
Q: a = (2,3), b = (−1,5). Find a·b, the angle between them, and the projection of a on b. a·b = −2+15 = 13. |a| = √13, |b| = √26. cosθ = 13/(√13·√26) = 13/√338 ≈ 0.707. θ ≈ 45°. Projection = 13/√26 = √(13/2) ≈ 2.55.