標題:
F2 奧數 plz
發問:
最佳解答:
Since x > 0, then x+ 1/x > = 2, then b= 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
其他解答:
可唔可以話看到 a=b=c?|||||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！|||||what is 彩虹?|||||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
F2 奧數 plz
發問:
此文章來自奇摩知識+如有不便請留言告知
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. 更新: F2 奧數 有Heron's formula, 不過好似用唔到. 更新 2: why 看到 a=b=c? steps 更新 3: CRebecca good answer! 不過我唔係好識證明Since x > 0, then x+ 1/x > = 2.最佳解答:
Since x > 0, then x+ 1/x > = 2, then b= 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
其他解答:
可唔可以話看到 a=b=c?|||||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！|||||what is 彩虹?|||||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
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