※ 引述《cuttlefish (总算要乖乖上课了)》之铭言： : 由於想赚一些ptt币 : 再加上不想让这里冷掉(虽然早就....) : 所以我想把一些我以前准备IMO做的题目po上来 : (有些应该是秒杀题吧~^^) : In triangle ABC , K and L are points on the side BC ( K being closer to B : than L ) such that BC KL = BK CL , and AL bisects KAC . Show that AL is : perpendicular to AB 我试着中文化好了@@ 三角形ABC中，K和L为BC边上的两点(是以B-K-L-C的顺序)使得BC乘KL=BK乘CL， 且AL平分角KAC。证明AL垂直AB。 不过...我不会做...|| -- 'Oh, Harry, dont't you see?' Hermione breathed. 'If she could have done one thing to make absolutely sure that every single person in this school will read your interview, it was banning it!' ---'Harry Potter and the order of the phoenix', P513 --

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