3.
如图所示,已知\(⊙O_{1}\)与\(⊙O_{2}\)相交于\(A\)、\(B\)两点,过点\(A\)作\(⊙O_{1}\)的切线交\(⊙O_{2}\)于点\(C\),过点\(B\)作两圆的割线,分别交\(⊙O_{1}\)、\(⊙O_{2}\)于点\(D\)、\(E\),\(DE\)与\(AC\)相交于点\(P\).
\((\)Ⅰ\()\)求证:\(AD/\!/EC\);
\((\)Ⅱ\()\)若\(AD\)是\(⊙O_{2}\)的切线,且\(PA=6\),\(PC=2\),\(BD=9\),求\(AD\)的长.