Vektor r= (½,k,¼) merupakan vektor satuan jika nilai k =

(1/2)^2 + k^2 + (1/4)^2 = 1
1/4 + k^2 + 1/16 = 1
k^2 + (4 + 1)/16 = 1
k^2 + 5/16 = 1
k^2 = 1 - 5/16
k^2 = (16 - 5)/16
k^2 = 11/16
k = √(11/16) atau k = -√(11/16)