论文部分内容阅读
许多数学问题与圆密切相关,解题中若能适当造圆,巧妙地运用圆的有关性质,可收到避繁就简的效果.掌握在怎样的条件下可以造圆且造怎样的圆是造圆解题的关键.这里介绍几种造圆的条件和方法,并举例加以说明.一、由定义造圆例1 过圆 x~2+y~2=r~2(r>0)外一点P(a,b)引圆的切线 PA、PB,A、B 是切点,求直线 AB 的方程.分析:因为从圆外一点 P 所引圆的切线PA 与 PB 长度相等,根据圆的定义可以 P 为圆心、PA 为半径造一个辅助圆,把问题转化为求
Many mathematical problems are closely related to the circle. If the circle can be properly created in the problem, and the relevant properties of the circle can be skillfully used, the effect of avoiding concision can be received. The conditions under which the circle can be created and what kind of circle is created are The key to creating a circle is to solve the problem. Here are several conditions and methods of creating a circle, and give examples to illustrate. First, by the definition of rounding example 1 round x~2+y~2=r~2(r>0) The tangents PA, PB, A, and B of the point P(a, b) are the tangent points. Find the equation of the straight line AB. Analyze: Because the tangents PA and PB of the circle drawn from the point P are the same, according to the circle The definition can make P a circle center and PA a radius to create an auxiliary circle and turn the problem into a