function [error result err einf]=ex1_3(q,f,front,rear,A,B,n)
format long   h=(rear-front)/n;
a=zeros(1,n+1);b=a;c=a;ff=a;x=linspace(front,rear,n+1);
b(1)=1;b(n+1)=1;
for j=2:n
      b(j)=2+h*h*q(x(j));a(j)=-1;c(j)=-1;
      ff(j)=h*h*f(x(j));
end
ff(1)=A;ff(n+1)=B;
u=zhuigan(a,b,c,ff,n+1);
U=sin(x);
plot(x,u,'r*',x,U,'b-');
legend('數值解','精確解');
xx=linspace(pi/16,pi*7/16,7);
jj=xx/h+1;
result=u(jj);
err=abs(result-U(jj));
einf=norm(err,inf);
error=abs(u-U);