Question

Найти cos a между c и d, если:

Answer 1

с = 2a + b = (2*2-1, 2*3+2, 0+1) =(3, 8, 1)

d= a -b = (2+1, 3-2, 0-1) = (3, 1, -1)

cos a = cd / |c||d|

cd = 9 + 8 - 1 = 16

|c| = √9 + 64 + 1 = √74

|d| = √9 + 1 + 1 = √11

cos a = 16/ √74*11