gausssinxy.m

利用高斯-勒让德多项式计算 sin(x+y)在矩形区域的积分

function xy = GaussSinxy(a,b,c,d,n)%a,b,c,d is the integrate area of x and y
                                   %firist Calculating the x-Gauss point
                                   %and W
p=legen_pw(n);
x = roots(p)';
x = sort(x);

for j=1:n
   y = zeros(1,n); 
   y(j)=1;
   p = polyfit(x,y,n-1); %多项式函数拟合
   P = poly_itg(p);      %求积
   w(j) = polyval(P,1) - polyval(P,-1);
   
end
xx=x;
x = 0.5*((b-a)*x + a + b);

for i=1:n
    %xy=ones(1,n);
   xy= 0.5*((d-c)*xx + c + d+2*x(i));
   % xy=x(i)*xy+xx;
    yy=feval('sin', xy);%求对应点的函数值
   y(i)=sum(w.*yy)*(d-c)/2;
end
xy = sum(w.*y)*(b-a)/2;
xy



    






 x = 0.5*((b-a)*x + a + b);%这里求的是Z