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發表 lcflcflcf 於 星期三 七月 26, 2006 1:27 am

由相似三角形
(R-d)/R=(d-r)/r
2Rr=Rd+dr
2Rr/Rrd=Rd/Rrd+dr/Rrd
2/d=1/r+1/R

[問題]幾何題17

發表 tangpakchiu 於 星期二 七月 25, 2006 11:43 pm

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