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《数学通报》(文[1])2008年2期问题1720为:△ABC中,以BC为轴(长轴或短轴均可)作一椭圆交AB于E,交AC于F(如图1).设M、N分别是点E、F关于直线BC的对称点,EN交FM于D.求证:AD⊥BC.
(In [1]), 2008 ISSUES Issue 1720 is: △ ABC, with BC as the axis (long axis or short axis can be) for an elliptical cross AB in E, AC AC in F (Figure 1). Let M and N be the points E and F, respectively, on the symmetry point of line BC.