5)“取极限” 2→>0≥M→ 定义△a的直径为 (△ak)=max{PP2|B2∈△ak} 令=max{(△Ok) <ksn z=f(r, y) V=imn∑f(5k,mk)△Gk k k Sk,lk5)“取极限” ( k ) = max P1P2 P1 ,P2  k 令 max ( )  1 k k n  =      = → =  n k k k k V f 1 0 lim ( , )   ( , ) k k f    k ( , )  k k