Vector of joining `P(x_(1),y_(1),z_(1))` and `P(x_(1),y_(1),z_(1))` is :
PQ = Position vector of Q - Position vector of P
`=(x_(2)hat(i) + y_(2)hat(j) + z_(2)hat(k)) - (x_(1)hat(i) + y_(1)hat(j) + z_(1)hat(k))`
`=(x_(2) - x_(1)) hat(i) + (y_(2) - y_(1))hat(j)+ (z_(2) - z_(1)) hat(k)`
Scalar component of PQ are `x_(2)-x_(1), y_(2) -y_(1), z_(2)-z_(1)`.
Magnitude of `vec(PQ)`
`|vec(PQ)| = sqrt((x_(2)-x_(1))^(2)+(y_(2)-y_(1))^(2)+(z_(2)-z_(1))^(2))`