i am trying to solve a 4 set of eqn for only two variables using loop and solve(), but it isnt working

%area(z) varies from z=1:101 but i need to specifically plot for interval (71<z<101)

%P2,P1,k,area@70, m2, At are known constants

%i only need to find mach(z) for corresponding area (z)

for z= 71:1:101

Eq1= AsAe(z)==(area(70)./area(z))*At;

Eq2= p2pe(z)==P2*P1*(1+0.5*(k-1)*mach(z).^2)^(k/(k-1));

Eq3= tet2(z)==(((1+0.5*(k-1)*mach(z).^2).^-1)*(1+0.5*(k-1)*m2^2)).^0.5;

Eq4= mach(z)==AsAe(z)*p2pe(z)*tet2(z)*m2;

S= solve([Eq1,Eq2,Eq3,Eq4],[mach]);

mach = double(S.mach);

mach(z)=mach;

end

figure(3);

plot(x,mach,'LineWidth',1.1);