function xia322(a,b,f,n)
fplot(f,[a,b],'g');
f1=inline(f);
hold on
x=linspace(a,b,n+1);
y=f1(x);
plot(x,y,'or')
hold on
xx=linspace(a,b,100);
yy=xia2(x,y,xx);
plot(xx,yy)
hold on