Geometry app warnings
05-06-2014, 05:32 AM
Post: #1
 Alberto Candel Member Posts: 169 Joined: Dec 2013
Geometry app warnings
In the Geometry Symbolic View I type

GA:=point(4, 3+e^(2*pi*i/5),3+e^(4*pi*i/5),3+e^(6*pi*i/5),3+e^(8*pi*i/5))
GB:=convexhull(GA)

then hit the Plot key and obtain a sequence of warnings like

Warning! Algebraic extension not implemented yet for poly[-1,0,30,-40,-5]

The numbers in brackets change.

Sometimes it stops and displays GB, which is a regular pentagon.

I cannot find an explanation for that warning in the User Guide. Any help? Thank you.

A.
05-06-2014, 06:46 AM
Post: #2
 parisse Senior Member Posts: 1,327 Joined: Dec 2013
RE: Geometry app warnings
This is because the convexhull is computed exactly, replacing exp() by sqrt, and simplifying in an unique algebraic extension of the rationals. You can avoid the warnings by using approx data.
Code:
 GA:=evalf(4, 3+e^(2*pi*i/5),3+e^(4*pi*i/5),3+e^(6*pi*i/5),3+e^(8*pi*i/5)); GB:=convexhull(GA);
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