Point multiplication formula: let a = (x 1, y 1, z 1), b = (x2, y2, z2), ab = x1x2+y1y2+z65438. Property 2: AB = BA satisfies the formula for finding the included angle of the multiplicative commutative law: Cos(θ) =ab/|a||b|, assuming that A and B are unit vectors, COS (θ) = AB-> θ=arccos(ab). The sign judgment of the multiplication result is AB & Ab=0, the angle is equal to 90, and vectors A and B are orthogonal; Ab<0, angle (90, 180), A and B vectors are basically opposite.