因为∠AOC+∠DOF
=2∠BOC+2∠DOE
=2(∠BOC+∠DOE)
=2(∠BOE-∠COD)
=2(m-n)
所以∠AOF=∠AOC+∠DOF+∠COD=2(m-n)+n=2m-2n+n=2m+n