Question

Построить векторы AB и CD и найти угол между ними, если A (3;1), B (7;4), C (3;2), D (6;6)

Answer 1

AB = (7-3; 4-1) = (4; 3)
|AB| = V(4^2 + 3^2) = V(16 + 9) = V(25) = 5
CD = (6-3; 6-2) = (3; 4)
|CD| = V(3^2 + 4^2) = V(9 + 16) = V(25) = 5
cos a = AB*CD / (|AB|*|CD|) = (4*3 + 3*4) / (5*5) = 24/25