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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于点F.设M、N分别是点E、F关于直线BC的对称点,EN交FM于点D,求证:AD⊥BC.
The “mathematical bulletin” (Article [1]) in 2008 issue 2 question 1720 is: In ABC, take BC as the axis (long or short axis can be) as an elliptical cross AB in E, AC in the point F. M and N are the symmetry points of points E and F with respect to the straight line BC. EN passes FM at point D to verify: AD ⊥ BC.