怎样只用直尺和圆规作平行线?
\u600e\u6837\u53ea\u7528\u76f4\u5c3a\u548c\u5706\u89c4\u4f5c\u5e73\u884c\u7ebf\u5176\u5b9e\uff0c\u53ea\u8981\u4f1a\u7528\u5c3a\u89c4\u4f5c\u5782\u7ebf\u5c31\u597d\u4e86\u3002
\u4ee5\u5df2\u77e5\u76f4\u7ebf\u4e0a\u4efb\u610f\u4e24\u70b9\u4e3a\u5706\u5fc3\u505a\u4e24\u4e2a\u76f8\u4ea4\u7684\u5706\uff0c\u8fc7\u4e24\u4ea4\u70b9\u7684\u76f4\u7ebf\u5c31\u662f\u5df2\u77e5\u76f4\u7ebf\u7684\u5782\u7ebf\uff0c\u7136\u540e\u5728\u6c42\u51fa\u7684\u76f4\u7ebf\u4e0a\u91cd\u590d\u4ee5\u4e0a\u8fc7\u7a0b\u5c31\u662f\u4e86\u2026\u2026
1\uff0c\u5148\u7528\u76f4\u5c3a\u753b\u4e00\u6761\u76f4\u7ebfAB\uff0c\u5f53\u505a\u5e95
2\uff0c\u5206\u522b\u4ee5\u76f4\u7ebf\u7684\u4e24\u4e2a\u7aef\u70b9A\uff0cB\u4e3a\u5706\u5fc3\uff0c\u4ee5\u4e00\u4e2a\u5b9a\u957f\u4e3a\u534a\u5f84\uff0c\u5206\u522b\u753b\u4e24\u7aef\u5706\u5f27
3\uff0c\u518d\u5206\u522b\u4ee5\u76f4\u7ebf\u7684\u4e24\u4e2a\u7aef\u70b9A\uff0cB\u4e3a\u5706\u5fc3\uff0c\u4ee5\u53e6\u5916\u4e00\u4e2a\u5b9a\u957f\u4e3a\u534a\u5f84\uff0c\u5206\u522b\u753b\u4e24\u7aef\u5706\u5f27
4\uff0c\u7b2c\u4e8c\u6b65\u548c\u7b2c\u4e09\u6b65\u5206\u522b\u753b\u7684\u5706\u5f27\u5728\u5de6\u53f3\u5747\u6709\u4e24\u4ea4\u70b9C,D
\u8fde\u63a5ABCD----\u7b49\u8170\u68af\u5f62
先做线段垂线AD，然后以AD为半径，画圆，然后做圆的切线
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