I'm trying to build my own version of an intersect three planes document. When three planes intersect in a line though, my intersection command seems to break. I have defined three planes named, p, q, and r. Then I defined two lines of intersection as:
Intersect(p,q)
Intersect(q,r)
This produces two lines named g and h respectively. When the intersection of the three planes is a point, the command
Intersect(g,h)
correctly produces the point of intersection. But when the intersection of the three planes is a line, then the command
Intersect(g,h)
outputs nothing.
I've attached my file, since I know I'm not communicating this well. I'm pretty low skilled here, so I apologize in advance if this question is easily remedied.
Thanks!
p.s. I am using Geogebra Classic 5 on my laptop.
The same question 
The output of a particular command has to be the same type - so it can't change between Point and Line.
What you can do is use Condition to Show Object to handle the different cases and show a point or line as appropriate.
So you can check if g and h are parallel (and also if they are equal)
"normal" les 2 droites g et h sont confondues leur "intersection" est une droite
je vous propose de faire apparaître un texte dans ce cas
The output of a particular command has to be the same type - so it can't change between Point and Line.
What you can do is use Condition to Show Object to handle the different cases and show a point or line as appropriate.
So you can check if g and h are parallel (and also if they are equal)
Thank you both so much! This was very helpful!
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