#### 7.66 Bug in geom3d-package in Maple V.5 (15.3.99)

##### 7.66.1 Arnold Zitterbart

Bug in the geom3d-package ! intersection(s,p1,p2) fails, if s is parallet to x1_x2_plane

> restart;
> with(geom3d):
> point(A,[4,9,3]):A=coordinates(A);

A = [4, 9, 3]

> point(B,[-2,5,3]):B=coordinates(B);

B = [-2, 5, 3]

> line(g,[A,B]);
g



g is obviously parallel to the x1_x2_plane

p1:= any plane containing g:

> point(C1,[2,6,7]):plane(p1,[A,B,C1]);

p1
p2:= any other plane containing g too:

> point(C2,[-3,6,9]):plane(p2,[A,B,C2]);

p2

> intersection(s,p1,p2);
s



but s is not the intersection-line:

> F:=FixedPoint(s):'F'=coordinates(F);

F = [0, 19/3, -3]

> IsOnObject(F,g);

false

> IsOnObject(F,p1);

false

> IsOnObject(F,p2);

false



The sign of the x3-coord has to be changed:

> point(F_new,[xcoord(F),ycoord(F),-zcoord(F)]);

F_new

> IsOnObject(F_new,g);

true

> IsOnObject(F_new,p1);

true

> IsOnObject(F_new,p2);

true



therefore: a new intersection-procedure has to be deļ¬ned:

> intersection_pp:=proc(g::symbol,p1::symbol,p2::symbol)
>    local P;
>    intersection(g,p1,p2);
>
point(P,[xcoord(FixedPoint(g)),ycoord(FixedPoint(g)),-zcoord(FixedPoint(g))]):

>    line(g,[P,ParallelVector(g)]);
> end;



Are there any other solutions to this problem ?

It is corrected with Maple 6. (U. Klein)