theorem Th12: :: AOFA_A00:17

for a1, a2, a3, a4, a5, a6, a7, a8, a9, a10 being object holds {a1} \/ {a2,a3,a4,a5,a6,a7,a8,a9,a10} = {a1,a2,a3,a4,a5,a6,a7,a8,a9,a10}