题目:(2014年福州)如图,在△ABC中,∠B=45°,∠ACB=60°.AB=3(1/2) 2,点D为BA延长线上的点,且∠D=∠ACB,圆O为△ACD的外接圆.(1)求BC的长;(2)求圆O的半径.解析:命题者令相似三角形的最小等角∠B=45°且重合.相等的两边BC亦重合,不相等的两边BA与BD部分重合,短边的端点A落在BD上,从而获得了△ACD,把△ACD与其外接圆组合成一个图形,令∠ACB=60°,AB=3(1/2)2,继而提出两个问 Title: (Fuzhou, 2014) As shown in Fig. 4, △ ABC has ∠B = 45 °, ∠ACB = 60 ° .AB = 3 (1/2) 2, point D is the point on BA extension line, and ∠D = ∠ACB, and circle O is the circumcircle of △ ACD. (1) Find the length of BC. (2) Find the radius of circle O. Analysis: The propositional person makes the minimum angle of similar triangles ∠B = 45 ° and overlap. BC on both sides also coincide, the two sides of the unequal BA and BD partially coincide, the short side of the endpoint A falls on the BD, resulting in △ ACD △ △ ACD and its circumcircle combined into a graph, so ∠ ACB = 60 °, AB = 3 (1/2) 2, then asked two questions