maka nilai Sin Alfa =

r = (2,4,4)
s = (1,-2,2)
|r| = akar [2^2 + 4^2 + 4^2]
= akar [4 + 16 + 16]
= akar 36
= 6
|s| = akar [1^2 + (-2)^2 + 2^2]
= akar [1 + 4 + 4]
= akar 9
= 3
r . s = 2×1 + 4×(-2) + 4×2
= 2 - 8 + 8
= 2
r . s = |r| |s| cos a
2 = 6 × 3 × cos a
2 = 18 × cos a
cos a = 2/18
cos a = 1/9