Diketahui A(4, 7, 0) , B(6, 10, -6) dan C(1, 9, 0) AB dan AC mewakili vektor u dan v. Besar sudut antara vektor u dan vektor v adalah...

AB = u = (6,10,-6)-(4,7,0) = [2,3,-6]
|u| = √4+9+36 = √49 = 7
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AC = v = (1,9,0)-(4,7,0) = [-3,2,0]
|v| = √9+4+0 = √13
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Cos a = u • v / |u| |v|
Cos a = 2.-3+3.2+-6.0 / 7√13
Cos a = -6 + 6 / 7√13
Cos a = 0
a = arc cos 0
a = 90 derajat

Semoga membantuu :)