8.
如图,已知\(AB\)是\(O\)的直径,\(AB=8\),点\(C\)在半径\(OA\)上\((\)点\(C\)与点\(O\)、\(A\)不重合\()\),过点\(C\)作\(AB\)的垂线交\(O\)于点\(D\),连接\(OD\),过点\(B\)作\(OD\)的平行线交\(O\)与点\(E\),交射线\(CD\)于点\(F\).
\((1)\)若弧\(ED=\)弧\(BE\),求\(∠F\)的度数;
\((2)\)设\(CO=x\),\(EF=y\),写出\(y\)与\(x\)之间的函数解析式,并写出自变量\(x\)的取值范围;
\((3)\)设点\(C\)关于直线\(OD\)的对称点为\(P\),若\(\Delta PBE\)为等腰三角形,求\(OC\)的长.