If a, b and c are side of triangle ABC, and
圖片參考：http://imgcld.yimg.com/8/n/HA00806376/o/20131012233903.jpg
Find the area of triangle ABC.
Help, 最好有 steps.
F2 奧數 plz
2013-10-13 7:40 am
回答 (5)
2013-10-14 7:58 am
✔ 最佳答案
Since x > 0, then x+ 1/x > = 2, thenb= 2a^2/(1+a^2)= 2a/(a+ 1/a) < = a
similarily, c=2b^2/(1+b^2) < = b, a=2c^2/(1+c^2) < = c
so b < = a < = c < = b, then a=b=c
2a^2/(1+a^2) = b= a, then a=1
the area of triangle ABC = sqrt(3) /4
2013-10-13 8:36 pm
可唔可以話看到 a=b=c?
2013-10-13 8:06 am
Can Heron's formula do something here.
2013-10-13 02:33:36 補充：
Sorry, 對 奧數 無甚認識，咁唔怪得要等啦！
2013-10-13 02:33:36 補充：
Sorry, 對 奧數 無甚認識，咁唔怪得要等啦！
2013-10-13 7:51 am
what is 彩虹?
2013-10-13 7:45 am
都係等彩虹啦～～～～
2013-10-13 01:34:43 補充：
但係中二應該未學 Heron's formula......
2013-10-13 02:39:07 補充：
大家咁話，我個人就等彩虹出現，但可能亦都有其他可以解答的會員～
^__^
2013-10-14 15:39:23 補充：
cas，呢個部份我則有能力幫幫你 (=^o^=)
For x > 0, √x is real.
(√x - 1/√x )² ≥ 0
x - 2√x (1/√x) + 1/x ≥ 0
x - 2 + 1/x ≥ 0
x + 1/x ≥ 2
2013-10-13 01:34:43 補充：
但係中二應該未學 Heron's formula......
2013-10-13 02:39:07 補充：
大家咁話，我個人就等彩虹出現，但可能亦都有其他可以解答的會員～
^__^
2013-10-14 15:39:23 補充：
cas，呢個部份我則有能力幫幫你 (=^o^=)
For x > 0, √x is real.
(√x - 1/√x )² ≥ 0
x - 2√x (1/√x) + 1/x ≥ 0
x - 2 + 1/x ≥ 0
x + 1/x ≥ 2
收錄日期: 2021-04-13 19:45:17
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20131012000051KK00260