请问这个怎么修改 ？

a=0.5;1-(x(1)-x(3))>0;
g=9.8;l=15;
k=sqrt(g/l);
N=a/g;
A=-2*N*sin(k/2*x(1));
P=A*sin(k*((60-0.5*x(1)*t3-0.25*x(3)^2-0.25*x(1)^2)/(0.5*x(1)))/2)-N;
Q=0.5^A*cos(k*((60-0.5*x(1)*x(3)-0.25*x(3)^2-0.25*x(1)^2)/(0.5*x(1))/2);
fx=@(x)(P*cos(k*x(3))+Q*sin(k*x(3))+N)^2+(Q*cos(k*x(3)-P*sin(k*x(3)))^2;
[xv,fv]=fminsearch(fx,[0,0])



错误使用 mupadmex
Error in MuPAD command: Index exceeds matrix dimensions.

出错 sym/subsref (line 687)
        B = mupadmex('symobj::subsref',A.s,inds{:});