Question

Given that 0.2i + 0.6j + ak is a unit vector . What is the value of a ?

Answer 1

The length of the vector should be 1. Therefore 

(0.2)^2 + (0.6)^2 + a^2 = 1^2 

a^2 = 1 - 0.04 - 0.36 = 0.6 

a = - sqrt(0.6) or a = sqrt(0.6)

Answer 2

given:
0.2i+0.6j+ak is unit vector
⇒√(0.04+0.36+a²)=1
⇒0.04+0.36+a²=1
⇒0.40+a²=1
⇒a²=1-0.40
⇒a²=0.6
⇒a=√0.6