theorem Th28: :: PARSP_2:28

for FdSp being FanodesSp
for a, b, c, d being Element of FdSp st parallelogram a,b,c,d holds
( not a,b,c are_collinear & not b,a,d are_collinear & not c,d,a are_collinear & not d,c,b are_collinear & not a,c,b are_collinear & not b,a,c are_collinear & not b,c,a are_collinear & not c,a,b are_collinear & not c,b,a are_collinear & not b,d,a are_collinear & not a,b,d are_collinear & not a,d,b are_collinear & not d,a,b are_collinear & not d,b,a are_collinear & not c,a,d are_collinear & not a,c,d are_collinear & not a,d,c are_collinear & not d,a,c are_collinear & not d,c,a are_collinear & not d,b,c are_collinear & not b,c,d are_collinear & not b,d,c are_collinear & not c,b,d are_collinear & not c,d,b are_collinear )