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