Which area does this trapz find?

Hello, So this is a code I used and the plot I obtained.

phi1=deg2rad(phiini);
phi2=deg2rad(phifin);
f=@(phi,x)[eqn1;eqn2];
[phi,xa]=ode45(f,[phi1:stepsize:phi2],[xini zini]);

I obtained 'xa' as the solution. The first and second column of 'xa' are X=xa(:,1); Z=xa(:,2);

I plotted the above as :

plot(Z,X) Now the question is if I apply trapz(Z,X) what area will be calculated. Can you shade the same for me? I need to be 100% sure that I am calculating the right area.

Thanks.