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# Intersection of a Cube with two planes and resulting polyhedron

Hi,

I am new to sage and trying to solve a problem where I have two planes cutting a cube. How can I find the resulting polytope/polyhedron as a result of this cut.

cube = polytopes.n_cube(3)
cube.Hrepresentation()

plane1 = Polyhedron(eqns=[(0,1,0,0)])
plane2 = Polyhedron(eqns=[(1,0,0,-1)])


Please also tell me that what is meant by eqns=[(0,1,0,0)] in sage? what equality it represent? similarly eqns=[(1,0,0,-1)] ?

Thanks

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## Comments

The last example in the documentation might be useful to understand what eqns means. http://x0.no/apde

## 2 Answers

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For an answer of the interpretation of eqns see your first post.

in order to calculate the intersection of your two planes and the cube, you can simply put all conditions in a new Polyhedron

cube = polytopes.n_cube(3)
plane1 = Polyhedron(eqns=[(0,1,0,0)])
plane2 = Polyhedron(eqns=[(1,0,0,-1)])
intersec=Polyhedron(eqns=plane1.equations()+plane2.equations(), ieqs=cube.inequalities())
print intersec.Hrepresentation()
intersec.show()

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## Comments

In a more recent version you can do:

sage: cube = polytopes.cube()
sage: plane1 = Polyhedron(eqns=[(0,1,0,0)])
sage: plane2 = Polyhedron(eqns=[(1,0,0,-1)])
sage: intersec = cube & plane1 & plane2


Thank you very much. Your explanation was very useful in solving my problem.

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Asked: 2013-02-19 00:21:51 +0200

Seen: 654 times

Last updated: Feb 20 '13