Question

Is the line through (4,1,-1) & (2,5,3) perpendicular to the liine through (-3,2,0)& (5,1,4)?

Answer 1

create 2 vectors from the givens points, and see what their dot product is

Answer 2

Thamks. Zero. Dot product. Angle pi halves.

Answer 3

(4,1,-1) (5,1,4)
-2-5-3 3-2 0
------ ------
2,-4,-4 8,-1,4

2,-4,-4
8,-1 ,4
--------
16+4-16 not = 0, so they aint perped

with any luck i did the mathing correctly :)