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+--- Thread: help with geometry app (/thread-1067.html)
help with geometry app - phgerin - 04-09-2014 07:58 AM
Hello all,
The following example works fine on GeoGebra but is failing on the HP Prime.
![[Image: HP1.jpg]](http://users.skynet.be/sky39147/HP1.jpg)
![[Image: HP2.jpg]](http://users.skynet.be/sky39147/HP2.jpg)
The last segment GO is never displayed.
It seems to occur each time I use the "inter" command to define a point.
So, where is the error ?
Thanks
RE: help with geometry app - parisse - 04-09-2014 09:09 AM
inter returns a list of points in GM, not a point. You should use single_inter instead of inter if you know that there is only one intersection point, or segment(GC,GM[0])
RE: help with geometry app - phgerin - 04-09-2014 09:49 AM
(04-09-2014 09:09 AM)parisse Wrote: inter returns a list of points in GM, not a point. You should use single_inter instead of inter if you know that there is only one intersection point, or segment(GC,GM[0])
Ok, thanks, it works with "single_inter" if I edit the command in the "symb" view.
In the "plot" view, with the drawing tools, why is the 3rd parametre of the command requiered ? Any way to skip it ?
RE: help with geometry app - parisse - 04-09-2014 10:23 AM
The 3rd parameter is used to choose one point if the intersection has more than 1 point, if this 3rd arg is a point, the intersection point is choosed nearest to the 3rd argument, if it is a list, the intersection point is choosed *outside* the list (this is useful if for example you intersect a line and a circle, you know one of the intersection and are interested in the 2nd intersection point).
I don't think you can skip it with the current interface, but it should indeed be possible to enhance the UI to skip it if the 2 objects to intersect are lines. Anyway, you can simply re-enter the last argument by pressing Enter if you intersect 2 lines, the argument will be ignored. And you can remove the 3rd arg from SYMB view later if you want to have a clean description of your construction (or directly enter single_inter(GA,GB) from SYMB view).