function out=f(theta)
L1=2;
L2=2^(1/2);
L3=L2;
gamma=pi/2;
p1=5^(1/2);
p2=p1;
p3=p1;
x1=4;
x2=0;
y2=0;
A2=L3*cos(theta)-x1;
B2=L3*sin(theta);
A3=L2*(cos(theta)*cos(gamma)-sin(theta)*sin(gamma))-x2;
B3=L2*(cos(theta)*sin(gamma)+sin(theta)*cos(gamma))-y2;
N1=B3.*(p2.^2-p1.^2-A2.^2-B2.^2)-B2.*(p3.^2-p1.^2-A3.^2-B3.^2);
N2=-A3.*(p2.^2-p1.^2-A2.^2-B2.^2)+A2.*(p3.^2-p1.^2-A3.^2-B3.^2);
D=2*(A2.*B3-B2.*A3);
out=N1.^2+N2.^2-p1.^2*D.^2;