function[y]=part3(L,t)
%A中的第三部分,與B有關(guān)的
%t=linspace(pi/2,pi,100);
%L=7;
%t=pi/100;
%k=0;
B=1;
if(mod(L,2)==0)
    y=((B.^(L+1))/pi)*(((-1).^(L/2))*sin(B*t)/(B*t)-(L/(B*t))*disanhanshu((B*t),(L-1)));
else
    y=((B.^(L+1))/pi)*(((-1).^(L/2))*cos(B*t)/(B*t)-(L/(B*t))*disanhanshu((B*t),(L-1)));
end

%for t=linspace(pi/2,pi,100);
    %y=(sin(B*t))/(pi*t);
   %while(k<L)
    %       k=k+1;
     %      if(mod(k,2)==0)
      %          y=((B.^(k+1))/pi)*(((-1).^(k/2))*sin(B*t)/(B*t)-(k/(B*t))*y)
      %   else
      %          y=((B.^(k+1))/pi)*(((-1).^((k-1)/2))*cos(B*t)/(B*t)-(k/(B*t))*y)
      %   end
      %end
%end