function value=poly_even(x,coeff,n);
m=double(int32(n/2));
if n~=2*m
    disp('Error in poly_even(x,coeff,n):')
    disp('The parameter n must be an even integer.')
end
xsp=x.*x;
value=coeff(m+1)*ones(size(x));
for i=m:-1:1
    value=coeff(i)+xsp.*value;
end
求偶次多项式逼近Sint x的值，一运行就出错，哪儿的问题？