altitude h = DE sin 60 = sqrt(3)/2 * DE

please refer to

http://mathworld.wolfram.com/EquilateralTriangle.html

所有跟帖: 

謝謝任教授沒笑話我...上幾年班以後把這些知識都全部還給老師了,汗顏! -陶陶樂,樂陶陶- 給 陶陶樂,樂陶陶 發送悄悄話 陶陶樂,樂陶陶 的博客首頁 (20 bytes) () 12/14/2009 postreply 16:35:51

Why didn't thank me?!!! -念親- 給 念親 發送悄悄話 念親 的博客首頁 (208 bytes) () 12/14/2009 postreply 18:53:13

回複:Why didn't thank me?!!! -陶陶樂,樂陶陶- 給 陶陶樂,樂陶陶 發送悄悄話 陶陶樂,樂陶陶 的博客首頁 (93 bytes) () 12/14/2009 postreply 21:34:40

回複:回複:Why didn't thank me?!!! -陶陶樂,樂陶陶- 給 陶陶樂,樂陶陶 發送悄悄話 陶陶樂,樂陶陶 的博客首頁 (49 bytes) () 12/14/2009 postreply 22:11:19

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