For a line there are different ways to define, that can be converted to each other:
Parameter form: 
; 
Pointform: The line is defined with the 2 points 
und .
Coordinates form in 2 dimensions: a x +b y=c
Conversion point form in parameter form
.
Conversion parameter form in pointform
; 
Conversion parameter form in coordinates form (2D)
----> -b2 x +b1 y = (a2 b1 – a1 b2)
Conversion coordinates form in parameter form (2D)
If a 0
;
else if b 0
;
else
parallel: Both vectors an
d a
re linear undependend. There is no l¹0 with .
