题目

—Whom would you for the job?—Tom, I think. He's always careful and serious. A . suggest B . remind C . remember D . explain 答案：A（2010•东莞）如图，PA与⊙O相切于A点，弦AB⊥OP，垂足为C，OP与⊙O相交于D点，已知OA=2，OP=4．（1）求∠POA的度数；（2）计算弦AB的长．