27.已知,∠MON=90°,點(diǎn)A在邊OM上,點(diǎn)P是邊ON上一動(dòng)點(diǎn),將線段AP繞點(diǎn)A逆時(shí)針旋轉(zhuǎn)60°,得到線段AB,連接OB,BP.
(1)如圖1,當(dāng)∠OAP=45°時(shí),試判斷OB與AP的位置關(guān)系:
;
(2)如圖2,當(dāng)∠OAP=60°,OA=2時(shí),求線段OB的長度;
(3)如圖3,將線段OB繞點(diǎn)O順時(shí)針旋轉(zhuǎn)60°,得到線段OC,連接PC,BC,請證明△ABO≌△PBC;
(4)如圖4,當(dāng)∠OAP=α?xí)r,在(3)的條件下,作CH⊥ON于點(diǎn)H.當(dāng)點(diǎn)P在射線ON上運(yùn)動(dòng)時(shí),用等式表示線段OA與CH之間的數(shù)量關(guān)系,并證明.