theorem Th35: :: BKMODEL2:46

for N1, N2 being invertible Matrix of 3,F_Real
for h1, h2 being Element of SubGroupK-isometry st h1 = homography N1 & h2 = homography N2 holds
( h1 * h2 is Element of SubGroupK-isometry & h1 * h2 = homography (N1 * N2) )