If I can draw a picture for you, you will understand immediately

回答: too hard for 米,嘻嘻周游列国逍遥人生2012-12-07 07:14:29

Try to draw 20, 13, 12 from same point (from left to right), they will make two right triangles with sharing sides on same line (base).

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谢谢。现在有点懂了::)) -周游列国逍遥人生- 给 周游列国逍遥人生 发送悄悄话 周游列国逍遥人生 的博客首页 (0 bytes) () 12/07/2012 postreply 07:45:50

学绘画图乐::)) -flagsix- 给 flagsix 发送悄悄话 (670 bytes) () 12/07/2012 postreply 13:36:13

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