众所周知,过圆外一点可以作圆的两条切线,数学竞赛中有一些问题涉及到过圆外一点可以作圆的两条切线的问题,常常使人措手不及,本文通过实例,利用点到直线的距离公式结合韦达定理解决这类问题,可以化繁为简,化难为易,现将它献给读者. As we all know, a circle outside the circle can be a tangent of two, mathematical contest has some problems involving the circle can be outside a circle of two tangent problems, often surprising, this article by example, the use of point to line From the formula to solve such problems with the Vedic theorem, it can be simplified and easy, and it is dedicated to readers.