题目

He is a responsible writer, and to be respected.(get something becauseof what you have done) 答案：【1】deserves如图，⊙A与x轴交于B（2，0）、（4，0）两点，OA=3，点P是y轴上的一个动点，PD切⊙O于点D，则PD的最小值是                ．