如图,在\(⊙O\)中,直径\(AB\)垂直弦\(CD\)于\(E\),过点\(A\)作\(∠DAF=∠DAB\),过点\(D\)作\(AF\)的垂线,垂足为\(F\),交\(AB\)的延长线于点\(P\),连接\(CO\)并延长交\(⊙O\)于点\(G\),连接\(EG\).
\((1)\)求证:\(DF\)是\(⊙O\)的切线;
\((2)\)若\(AD=DP\),\(OB=3\),求\( \overparen {BD}\)的长度;
\((3)\)若\(DE=4\),\(AE=8\),求线段\(EG\)的长.