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).
If I can draw a picture for you, you will understand immediately
所有跟帖:
• 谢谢。现在有点懂了::)) -周游列国逍遥人生- ♂ (0 bytes) () 12/07/2012 postreply 07:45:50
• 学绘画图乐::)) -flagsix- ♂ (670 bytes) () 12/07/2012 postreply 13:36:13