在\(Rt\triangle ABC\)中, \(∠ACB=90^{\circ}\),\(CD\)是\(AB\)边的中线,\(DE⊥BC\)于\(E\), 连结\(CD\),点\(P\)在射线\(CB\)上\((\)与\(B\),\(C\)不重合\()\).
\((1)\)如果\(∠A=30^{\circ}\)
\(①\)如图\(1\),\(∠DCB= \)_________\({\,\!}^{\circ}\)
\(②\)如图\(2\),点\(P\)在线段\(CB\)上,连结\(DP\),将线段\(DP\)绕点\(D\)逆时针旋转\(60^{\circ}\),得到线段\(DF\),连结\(BF\),补全图\(2\)猜想\(CP\)、\(BF\)之间的数量关系,并证明你的结论;
\(( 2 )\)如图\(3\),若点\(P\)在线段\(CB\) 的延长线上,且\(∠A=\alpha \) \((0^{\circ} < \alpha < 90^{\circ})\) ,连结\(DP\), 将线段\(DP\)绕点逆时针旋转\(2\alpha \)得到线段\(DF\),连结\(BF\), 请直接写出\(DE\)、\(BF\)、\(BP\)三者的数量关系\((\)不需证明\()\).