Re: 哪位大侠能帮忙看看# EE - 电子工程
c*r
1 楼
d(a,b) + d(c,d) ≤ d(a,c)+d(c,b) + d(c,b)+d(b,d) (3)
= d(a,c)+d(b,d) if d(c,b)=0 => c=b.
OR
d(a,b) + d(c,d) ≤ d(a,d)+d(d,b) + d(c,b)+d(b,d) (3)
= d(a,d)+d(b,c) if d(b,d)=d(d,b)=0 => b=d.
OR
.... a=c.
OR
.... a=d.
OR .... a=b, c=d.
=> Any two are equal.