A=Pi+oj+ rk OP O0 OR V·A 十 diva ax ay az V×A= = rotAl O R 若P,Q,R具有连续的二阶偏导数,即得 div(rota)=0 -即旋度场是无源场 rot(gradu =0 即梯度场是无旋场A Pi Qj Rk = + + divA z R y Q x P A = + + = rotA P Q R x y z i j k A = = 若 P,Q , R 具有连续的二阶偏导数, 即得 div(rotA) = 0 ---------即旋度场是无源场 ( ) 0 rot gradu = ---------即梯度场是无旋场