Diketahui a+b=i-j+4k dan |a-b|= akar 14 hasil dari a.b=...

a+b = i - j + 4k = (1,-1,4)
|a-b| = akar 14
|a+b| = akar [1^2+(-1)^2+4^2]
= akar [1+1+16]
= akar 18

|a+b|^2 = |a|^2 + |b|^2 + 2|a||b|cos a
|a-b|^2 = |a|^2 + |b|^2 - 2|a||b|cos a
____________________________ _
18 - 14 = 4|a||b|cos a
4 = 4|a||b|cos a
4/4 = |a||b|cos a
|a||b|cos a = 1
a.b = |a||b|cos a = 1
Jadi a.b = 1