:: deftheorem Def03 defines (*) BKMODEL3:def 4 :
for h1, h2, b₃ being Element of EnsLineHomography3 holds
( b₃ = h1 (*) h2 iff ex N1, N2 being invertible Matrix of 3,F_Real st
( h1 = line_homography N1 & h2 = line_homography N2 & b₃ = line_homography (N1 * N2) ) );