证明:考虑|x2-x1|∈[0,0.5]或[0.5,1]两种情况
若|x2-x1|∈[0,0.5],则|f(x2)-f(x1)|<|x2-x1|≤1/2
若|x2-x1|∈[0.5,1],不妨设x1<x2,则0≤x1≤0.5≤x2≤1
故|f(x2)-f(x1)|=|f(x2)-f(1)+f(0)-f(x1)|
≤|f(x2)-f(1)|+|f(x1)-f(0)|
<|x2-1|+|x1-0||
=1-x2+x1≤1/2
证明:考虑|x2-x1|∈[0,0.5]或[0.5,1]两种情况
若|x2-x1|∈[0,0.5],则|f(x2)-f(x1)|<|x2-x1|≤1/2
若|x2-x1|∈[0.5,1],不妨设x1<x2,则0≤x1≤0.5≤x2≤1
故|f(x2)-f(x1)|=|f(x2)-f(1)+f(0)-f(x1)|
≤|f(x2)-f(1)|+|f(x1)-f(0)|
<|x2-1|+|x1-0||
=1-x2+x1≤1/2