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01-20-12, 10:20 PM | #1 |
God of Gamer
魔法學園學生
註冊日期: Aug 2003
文章: 6,840
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幾何問題
兩個同心圓 C1(半徑=r), C2(半徑=s) C2的面積是C1的兩倍 求 r與s的比例
引申問題: 類似上面的一對相似正多邊形的邊長關係 例如: a) 等邊三角形 T1 (邊長=p), T2(邊長=q) T2的面積是T1的兩倍 求 p與q的比例 b) 正方形 S1 (邊長= y), S2(邊長=z) S2的面積是S1的兩倍 求y與z的比例 c) 如此類推 由一對等邊三角形開始 增加邊數成各對正多邊形 直至圓形 各對邊長的關係是否形成相關函數? |
01-20-12, 11:02 PM | #2 |
Crazy Gamer
paper lion
註冊日期: Jul 2009
文章: 1,220
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let the area of C1 be a = pi r^2
let the area of C2 be A = pi s^2 As C2的面積是C1的兩倍, A = 2a 2pi r^2 =pi s^2 (s/r)^2 = 2 s/r = sqrt 2 the rest is similar.
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01-21-12, 02:27 AM | #3 |
The One
註冊日期: Mar 2002
文章: 20,716
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The ratio of similar 2D figures = (the ratio of a pair of corresponding lengths of the figures)^2
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