求助各位朋友，急急急，希望大神帮忙啊！
 

syms Dd Dd0 x y z Wn theta Ue Ve n s
Dd0=10^(-3);
Wn=(2*n+1).*pi.*x.*Dd0/(3.6);
Dd=Dd0.*tanh(1.76.*sqrt((1/x)-1));
Ue=sqrt((1+sqrt(1+(Dd^2.*(sin(2.*theta)).^2)/(Wn.^2)))/2);
Ve=sqrt((1-sqrt(1+(Dd^2.*(sin(2.*theta)).^2)/(Wn.^2)))/2);
z=(Dd^2.*(sin(2.*theta)).^2.*exp(-2.*Wn.*cos(theta).*0.1))/(sqrt(Wn.^2+Dd.^2.*(sin(2.*theta)).^2))*(Ue.^4+Ve.^4.*exp(-4.*Wn.*cos(theta).*0.1));
s=subs(int(z,theta,-pi/2,pi/2))
y=symsum(s,n,1,1000)
ezplot(y,[0,1])


为什么运行不了，错误在哪里啊。希望大家帮忙啊，非常感谢啊！