function out=f_4(theta) L1=3;L2=3*sqrt(2);L3=L1; p1=5;p2=p1;p3=3; x=1;y=2; x1=5; x2=0;y2=6; gamma=pi/4; A2=L3*cos(theta)-x1; B2=L3*sin(theta); A3=L2*cos(theta+gamma)-x2; B3=L2*sin(theta+gamma)-y2; D=2*(A2*B3-B2*A3); 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); out=N1^2+N2^2-p1^2*D^2;