read `C:\\RENE.txt`:


Sqabcd:=proc(a,b,c,d):
evalb(
expand(
simplify(
expand(
-4*c^3*d+6*c^2*d^2-4*c*d^3-4*a*c^3-4*a*d^3-4*b^3*c-4*b^3*d+6*b^2*c^2+6*b\
^2*d^2-4*b*c^3-4*b*d^3-4*a^3*b-4*a^3*c-4*a^3*d+6*a^2*b^2+6*a^2*c^2+6*a^2\
*d^2-4*a*b^3-40*a*b*c*d+4*a^2*b*d+4*a^2*b*c+4*a*b^2*d+4*a*b^2*c+4*a^2*c*\
d+4*a*b*c^2+4*a*c*d^2+4*a*c^2*d+4*a*b*d^2+4*b^2*c*d+4*b*c*d^2+4*b*c^2*d+\
a^4+b^4+c^4+d^4)))=0):
end:


Sadov:=proc() local P,i,t,R,A,B,C,D,a,b,c,d,p,q: 
for i from 1 to 4 do 
P[i]:=ParamCircle([0,0],R,t[i]): od: 
A:=P[1]:B:=P[2]:C:=P[3]:D:=P[4]:

a:=DeSq(A,B):
b:=DeSq(B,C):
c:=DeSq(C,D):
d:=DeSq(D,A):
p:=DeSq(A,C):
q:=DeSq(B,D):

Sqabcd(a*b*p,c*d*p,b*c*q,a*d*q):

end: