用圆规找出线段 AB中点。不能用直尺。
作者：零加一中+-
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这个应该比较难，书上说是“Challenge”。
这个应该比较难，书上说是“Challenge”。
Let R = AB From A draw acr1 with r = R. From B draw arc2 with r = R. arc1 and arc2 meet at C. From C draw arc3 with r = R. arc3 and arc2 meet at D. From D draw arc4 with r = R. arc4 and arc2 meet at E. E is on AB and EB = R. From E draw arc5 wirg r = 2R. arc1 and arc5 meet at F. From F draw arc6 with r = R. arc6 meets AB at M. ∆EFA ~ ∆FAM by AA. They are both isosceles with same base angles. ∆EFA has 3 sides 2R, 2R, R. ∆EFA should have 3 sides R, R, R/2. |