90=∠EDC=∠EAB
ΔABC~ΔDEC
設AE=CD=x
12/x=(30+x)/(12+x)
x=6
∠ECD=60
∠ABD=30
∠AO1D=60
☉O1直徑=12√7
arcAD=12√7*pi*60/360=2√7*pi
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由 lcflcflcf 於 星期六 七月 29, 2006 6:31 pm
[問題]幾何題37
由 tangpakchiu 於 星期六 七月 29, 2006 3:11 pm
#ed_op#DIV#ed_cl##ed_op#IMG alt="image file name: 2k470bf5f8dd.gif" src="http://yll.loxa.edu.tw/phpBB2/richedit/upload/2k470bf5f8dd.gif" border=0#ed_cl##ed_op#/DIV#ed_cl##ed_op#DIV#ed_cl##ed_op#FONT face=新細明體#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#△#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#ABC#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#頂點分別在☉#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#O1，#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#☉#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#O2#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#上，兩圓交於#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#D#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#和#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#E#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#兩點，#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#EC#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#為☉#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#O2#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#直徑，#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#AC#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#過#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#E#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#點，#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#BC#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#過#ed_op#/SPAN#ed_cl##ed_op#SPAN lang=EN-US#ed_cl#D#ed_op#/SPAN#ed_cl##ed_op#SPAN style="mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"#ed_cl#點，AE=DC，若EC=12cm，BD=30cm，求arcAD的長。#ed_op#/SPAN#ed_cl##ed_op#/FONT#ed_cl##ed_op#/DIV#ed_cl#