theorem Th15: :: CIRCCOMB:15

for S1 being non empty ManySortedSign
for S2, S being non empty non void Circuit-like ManySortedSign st S = S1 +* S2 holds
for v2 being Vertex of S2 st v2 in InnerVertices S2 holds
for v being Vertex of S st v2 = v holds
( v in InnerVertices S & action_at v = action_at v2 )