高考对平面几何题的考查常常以选做题的形式出现,而且多是围绕圆而编制。解决这类题目常常会用到几何证明选讲中所补充的内容,即四点共圆、圆内接四边形、弦切角定理、切割线定理及相交弦定理等。下面,笔者着重探讨这类题的解法,与读者交流。问题1:如图1,P是☉O外一点,A为切点,割线PBC与☉O相交于点B、C,PC=2PA,D为PC的中点,AD的延长线交☉O于点E。 Examination of the college entrance examination on the geometric problems often appear in the form of election questions, but mostly around the circle and preparation. To solve such problems often use the geometric proof of the supplement to say that four-point total circle, circular quadrilateral, chord cut theorem, cutting line theorem and the intersection of chord theorem and so on. The following, the author focuses on the solution of such questions, and readers exchange. Problem 1: As shown in Figure 1, P is a point outside ☉O, A is a tangent point, the severance PBC and ☉O intersect at point B, C, PC = 2PA, D is the midpoint of PC, and the extension of AD is ☉O At point E.