theorem Th13: :: FUNCTOR3:13

for A, B, C being non empty transitive with_units AltCatStr
for F1, F2, F3 being covariant Functor of A,B
for G1 being covariant Functor of B,C
for p being transformation of F1,F2
for p1 being transformation of F2,F3 st F1 is_transformable_to F2 & F2 is_transformable_to F3 holds
G1 * (p1 `*` p) = (G1 * p1) `*` (G1 * p)