TXM797: RATIONAL CYCLIC-POLYGON

In[]:=
Manipulate[Module[{AA,BB,CC,MM},AA={y(x^2+1),0};​​BB={(x(x+y)^2-x(xy-1)^2)/(x^2+1),(2x(x+y)(xy-1))/(x^2+1)};​​CC={0,0};​​MM={((y+z)(yz-1)(x^2+1)(z^2-1))/(z^2+1)^2,(2z(y+z)(yz-1)(x^2+1))/(z^2+1)^2};​​Graphics[{Point/@{AA,BB,CC,MM},Text["A",AA],Text["B",BB],Text["C",CC],Text["M",MM],Circumsphere[{AA,BB,CC}]}]],{x,-10,10},{y,-10,10},{z,-10,10},SaveDefinitionsTrue]
Out[]=
​
x
y
z

Caption​An cyclic polygon is called rational if it has a rational area and the distance between any two of its vertices is also rational. In the general case, suppose we have Cartesian coordinates of 3 vertices
A=(y(
2
x
+1),0)
,
B=
2
x(x+y)
-
2
x(xy-1)
2
x
+1
,
2x(x+y)(xy-1)
2
x
+1
,
C=(0,0)
. Then the coordinates of all remaining vertices of the rational polygon are determined through a parameter
z
n
as
M
n
=
(y+
z
n
)(
yz
n
-1)(
2
x
+1)(
2
z
n
-1)
2
(
2
z
n
+1)
,
2
z
n
(y+
z
n
)(
yz
n
-1)(
2
x
+1)
2
(
2
z
n
+1)

. For all
x,y,
z
n
∈Q
.

Author: Minh Trinh Xuan​
​