function [ X, Y ] = closed_link_constraints ...
( theta1, theta2, theta3, theta4, l1, l2, l3, l4, x1, y1, x3, y3 )
% •ÂƒŠƒ“ƒN‹@�\ �§–ñ‚Ì’l
    C1 = cos(theta1); S1 = sin(theta1);
    C12 = cos(theta1+theta2); S12 = sin(theta1+theta2);
    C3 = cos(theta3); S3 = sin(theta3);
    C34 = cos(theta3+theta4); S34 = sin(theta3+theta4);
    X = l1*C1+l2*C12+x1 - (l3*C3+l4*C34+x3);
    Y = l1*S1+l2*S12+y1 - (l3*S3+l4*S34+y3);
end
