function T=denavit(t,d,a,A)
T=[ cos(t) -sin(t)*cos(A)  sin(t)*sin(A) cos(t)*a;
    sin(t)  cos(t)*cos(A) -cos(t)*sin(A) sin(t)*a;
    0       sin(A)         cos(A)        d;
    0       0              0             1];