Given the points

A(1,-1,1),B(2,1,0)

and

C(0,2,-1)

in the third dimension\ and

D

a point in third dimension too with coordinates

(x,y,0)

. Find:\ 2.1.

AB

and

BC_()

.

4. Given the points A(1,1,1),B(2,1,0) and C(0,2,1) in the third dimension and D a point in third dimension too with coordinates (x,y,0). Find: 4.1. AB and BC