※ 引述《cuttlefish (總算要乖乖上課了)》之銘言： : 由於想賺一些ptt幣 : 再加上不想讓這裡冷掉(雖然早就....) : 所以我想把一些我以前準備IMO做的題目po上來 : (有些應該是秒殺題吧~^^) : 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 我試著中文化好了@@ 三角形ABC中，K和L為BC邊上的兩點(是以B-K-L-C的順序)使得BC乘KL=BK乘CL， 且AL平分角KAC。證明AL垂直AB。 不過...我不會做...|| -- '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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