题目

Your computer has been playing music for years, one CD at a time. Now hundreds of songs can be stored in your PC if they' re in the MP3 format (格式). What is it? MP3 compressed(压缩) music into small computer files. You may download MP3 music several ways: Music can be downloaded from websites that have turned wide music libraries into MP3. Once MP3 music is on your PC’s hard drive, you can play it through your computer's speakers, burn it onto blank CDs or swap(交换) MP3 files with friends using e -mail. How much? Software needed to play and convert MP3 music is often free. Compact如图，△ABC中，∠ACB=90°，D为AB上一点，以CD为直径的⊙O交BC于点E，连接AE交CD于点P，交⊙O于点F，连接DF，∠CAE=∠ADF．（1）判断AB与⊙O的位置关系，并说明理由；（2）若PF：PC=1：2，AF=5，求CP的长．