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如图,\(\triangle PAD\)是边长为\(3\)的等边三角形,四边形\(ABCD\)为正方形,平面\(PAD⊥\)平面\(ABCD\),点\(E\),\(F\)分别为\(CD\),\(PD\)上的点,且\( \dfrac {PF}{FD}= \dfrac {CE}{ED}= \dfrac {1}{2}\),点\(G\)为\(AB\)上的一点,且\( \dfrac {AG}{GB}=λ\).
\((1)\)当\(λ= \dfrac {1}{2}\)时,求证:\(PG/\!/\)平面\(AEF\);
\((2)\)当\(FG⊥AC\)时,求三棱锥\(A-EFG\)的体积.