Plotting 2 functions with respect to each other

I defined the following functions:

function alpha = error1(T)
syms x y
P0 = 1/(2*pi*0.6)*exp(-1/(2*0.36)*(x^2+y^2-2*0.8*x*y));
P1 = 1/(2*pi*1)*exp(-1/(2*1)*(x^2+y^2));
L1 = int(P1,x,-inf,0)/int(P0,x,-inf,0);
L2 = int(P1,x,0,+inf)/int(P0,x,0,+inf);
I1 = int(P0,x,-inf,0);
I2 = int(P0,x,0,+inf);

alpha = int(I1,y,L1>T)+ int(I2,y,L2>T);
end

function beta = error2(T)
syms x y
P0 = 1/(2*pi*0.6)*exp(-1/(2*0.36)*(x^2+y^2-2*0.8*x*y));
P1 = 1/(2*pi*1)*exp(-1/(2*1)*(x^2+y^2));
L1 = int(P1,x,-inf,0)/int(P0,x,-inf,0);
L2 = int(P1,x,0,+inf)/int(P0,x,0,+inf);
I1 = int(P1,x,-inf,0);
I2 = int(P1,x,0,+inf);

beta = int(I1,y,L1<T)+ int(I2,y,L2<T);
end

I don't if there's a problem in the expressions of alpha and beta, but what I mean is that Im trying to integrate I1 for example over the domain L1(y) < T.

After that I defined:

t = 0:0.01:30;
y1 = error1(t);

I get the following error:

Error using mupadmex
Error in MuPAD command: The argument is invalid. [Dom::Interval::new]

Error in sym/int (line 124)
   rSym = mupadmex('symobj::intdef',f.s,x.s,a.s,b.s,options);

Error in error2 (line 10)
beta = int(I1,y,L1<T)+ int(I2,y,L2<T);

[Walter Roberson]

merged into http://uk.mathworks.com/matlabcentral/answers/218141-defining-and-plotting-2-parametric-functions