Question

Vektor u= 2i+aj+k dan v = 4j-2j-2k saling tegak lurus maka nilai a adalah

Answer 1

U . v = |u||v| cosα

tegak lurus = 90 derajat
karena cos90 = 0, maka :

u . v = 0

(2*4) + (a*-2) + (1*-2) = 0
8 - 2a - 2 = 0
-2a + 6 = 0
-2a = -6
2a = 6
a = 6 / 2
a = 3

Answer 2