xmax is scalar floating function ?

%double Integrals

syms x y
fun=input('Enter the function f(x,y)=');
x1=input('Enter the outer integral lower limit:');
x2=input('Enter the outer integral upper limit:');
y1=input('Enter the inner integral lower limit:');
y2=input('Enter the inner integral upper limit:');
A=integral2(fun,x1,x2,y1,y2); 
disp(' Integral value is =')
disp(A)

output

%Enter the function f(x,y)=@(x,y) x.*y
%Enter the outer integral lower limit:0
%Enter the outer integral upper limit:a
%Enter the inner integral lower limit:@(x) x.^2
%Enter the inner integral upper limit:@(x) 2-x

%Error using integral2 (line 80)
%XMAX must be a floating point
%scalar.

Answer 1

[dpb]

...
%Enter the outer integral upper limit:a
...

a isn't defined above; it must be a numeric value; you passed the character 'a'

Answer 2

[Jan]

See: https://www.mathworks.com/help/matlab/ref/integral2.html#btbbuxy-1-xmax

integral2() expects the limits to be floating point numbers. Then @(x) x.^2 and @(x) 2-x are not matching, because these are function handles.