You must call TRc with a numerical input vector for v to get a plot.
v = linspace(1,20,100);
fval = TRc(v);
plot(v,fval)
function fval=TRc(v)
rho=1.225; %kg/m^3
s=47; %m^2
AR=6.5; %unitless
e=0.87; %unitless
w=103047; %N
cd0=0.032; %unitless
ET=40298; %N%engine thrust
PA=2*ET; %N
cl = (2*w)./(v.^2*rho*s); %lift coefficient
cd=cd0+(cl.^2/(pi*e*AR)); %drag coefficient
TR=w./(cl./cd); %N
PR=TR.*v; %W
fval=(PA-PR)./w;
end
