27.在四面体ABCDABCDABCD中,AD⊥AD\botAD⊥底面ABCABCABC,AB=AC=10AB=AC=\sqrt{10}AB=AC=10,BC=2BC=2BC=2,点GGG为三角形ABCABCABC的重心,若四面体ABCDABCDABCD的外接球的表面积为2449π\frac{244}{9}\pi9244π,则tan∠AGD=(\tan \angle AGD=(tan∠AGD=( )))