(u(1)*u(6)-u(3)*u(4))/(u(1)*u(5)-u(2)*u(4))
(u(3)*u(5)-u(2)*u(6))/(u(4)*u(5)-u(2)*u(4))

a: (m1+m2)*l1^2
b: m2*l1*l2*(sin(u(1))*sin(u(3))+cos(u(1))*cos(u(3)))
c: -1*(m2*l1*l2*(sin(u(1))*cos(u(3))-cos(u(1))*sin(u(3)))*(u(4))^2+(m1+m2)*gl1*sin(u(1))+k1*l1^2*u(2)+k2*l1*l2*(sin(u(1))*sin(u(3))+cos(u(1))*cos(u(3)))*u(4))
e: m2*l2^2
d: m2*l1*l2*(sin(u(1))*sin(u(3))+cos(u(1))*cos(u(3)))
f: -1*(m2*l1*l2*(cos(u(1))*sin(u(3))-sin(u(1))*cos(u(3)))*(u(2))^2+m2*gl2*sin(u(3))+k2*l2^2*(u(4))+k2*l1*l2*(sin(u(1))*sin(u(3))+cos(u(1))*cos(u(3)))*(u(2)))