With some examples in plane geometry, the author indroduces how to use Desargues theorem to simplify the proofs of problems of collinear points and concurrentlines.
利用代沙格定理及其逆定理 ，对平面几何的几个共线点和共点线的问题给出简捷的证法。
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Directed against the complexity of scheme design system of modularized flexible production lines an object oriented concurrent design system has been studied.