for C being Category
for a, b, c being Object of C
for i1 being Morphism of a,c
for i2 being Morphism of b,c st Hom (a,c) <> {} & Hom (b,c) <> {} & c is_a_coproduct_wrt i1,i2 & Hom (a,b) <> {} & Hom (b,a) <> {} holds
( i1 is coretraction & i2 is coretraction )