高观点下的初等数学（5）原创 林根数学 林根数学 今天关于二次曲线系，有下面的定理：定理如果已知两直线Li≡aix +biy+ci=0(i=1,2)和一条二次曲线f(x,y)=0，那么含有一个参数λ的方程f(x,y)+λL₁L₂=0，①是表示经过两直线与二次曲线的交点的二次曲线系
美国布朗大学的已故应用数学教授、写过一本巨著《古今数学思想》的克莱因 ，对于课堂教学有过一段精辟论述和殷切期待，他的英文原话是:“I would urge every teacher to become an actor. His classroom technique must be enlivened by every device used in theatre. He can be and should be dramatic where appropriate. He must not only have facts but fire. He can utilize even eccentricities of behavior to stir up human interest. He should not be afraid of humor and should use it freely. Even an irrelevant joke or story perks up the class enormously.”
