How can i pass this showed error ?

when i typed this following code an error is existed , what the solution of this ?

code :

clc;clear;clf 
To=288 ; Tx=285 ; Px=98000 ; k=1.4 ; R=287 ; Cp=1005 ;
%Getting Mx from To/Tx 
Mx=sqrt(2/(k-1)*((To/Tx)-1)) ; 
%Getting Mass flux which is constant for x,y 
%Mass conservation equation 
roV_y=Px/(R*Tx)*Mx*sqrt(k*R*Tx) ;
Py=10000:2000:40000 ; %downstream pressure values in pa 
%solving the equation to find Ty 
%energy conservation equation 
temp=solve('To=Ty+(roV_y)^2/(2*cp)*(R*Ty/Py)^2','Ty'); 
Ty=subs(temp);
%as the eqn. was 2nd order Ty will have +ve , -ve values 
%we will take the second row which is +ve values 
Tyy=Ty(2,:) ;
%calculating delta s 
delta_s=Cp*log(Tyy/Tx)-R*log(Py/Px) ;
%plotting fanno line 
plot(delta_s,Tyy,'r')
xlabel('\delta s (J/Kg.k)','fontsize',17) 
ylabel('Temp.(K)','fontsize',17)
hold on 
%plotting rayleigh line 
Py=10000:2000:40000 ; %downstream pressure values in pa 
%solving the eqn. to find Ty
%Momentum conservation eqn. 
temp1=solve('Px+(roV_y)^2*(R*Tx/Px)=Py+(roV_y)^2*(R*Ty/Py)','Ty');
Ty1=subs(temp1) ;
delta_S1=Cp*log(Ty1/Tx)-R*log(Py/Px) ;
plot(delta_S1,Ty1)
legend('Fanno line','Rayleigh line') 

Error :

Error using plot
Conversion to double from sym is not possible.

Error in Untitled (line 19)
plot(delta_s,Tyy,'r')