green's theorem

clc 
clear all
close all
syms x y r theta
F=input("enter the vecotr in terms of i j k")
integrand=diff(F(2),x)-diff(F(1),y);
polarint=r*subs(integrand,[x,y],[r*cos(theta),r*sin(theta)])
sol=int(int(polarint,r,0,3),theta,0,2*pi)
P=inline(vectorize(F(1)),'x','y')
Q=inline(vectorize(F(2)),'x','y')
x=linspace(-3.2,3.2,10);
y=x;
[X,Y]=meshgrid(x,y);
U=P(X,Y);
V=Q(X,Y);
quiver(X,Y,U,V)
hold on 
fplot(3*cos(theta),3*sin(theta),[0 2*pi])
axis equal