Question Number 6641 by WAI LIN last updated on 07/Jul/16
$${Q}\left(\mathrm{1}\right)\:{Express}\:{div}\:{A}\:=\:\bigtriangledown\:.\:{A}\:{in}\:{orthogonal}\:{coordinates}. \\ $$$${Q}\left(\mathrm{2}\right)\:{Express}\:\bigtriangledown^{\mathrm{2}} \:\phi\:{in}\:{orthogonal}\:{curvilinear}\:{coordinates}. \\ $$$${Q}\left(\mathrm{3}\right)\:{Express}\:\left({a}\right)\:\bigtriangledown\:×\:{Aand}\:\left({b}\right)\:\bigtriangledown^{\mathrm{2}} \phi\:{in}\:{spherical}\:{coordinates}. \\ $$