IfD,is nonsingular,.that isΦ，≠0 Time derivative of equations (g,t)=0I leads to (q,4,)=D,9+④，=0 更，9=-D,=v Time derivative of equations (g,t)=0 leads to 市=④，i+(中，)，1+D,i+亚g9+D:=0 Φ，i=Y Y=-(Φ，)m9-2Φ9-Φa TΦ nhx1 nhxncTime derivative of equations qt  0 leads to      0 t  q,q,t qq  Time derivative of equations q q,t  0 leads to         0     t t tt q q q q q q q q q q       ( )  q   q    t tt   ( qq)q q  2 q q  1 2 2           nh i tt t   1          nh i t t   nh nc j i q          q   nh nc nc k k k i j q q q                   1    q q  q q v q   t  If q is nonsingular, that is q  0