解析几何中求切线长最大值（前略）E:(x^2)/4+y^2=1,设直线l与圆C:x^2+y^2=R^2(1_数学解答

解析几何中求切线长最大值
（前略）E:(x^2)/4+y^2=1,设直线l与圆C:x^2+y^2=R^2(1

人气：495 ℃　时间：2020-10-02 04:47:29

解答

设B(a,b)则AB:ax/4+yb=1设A(m,n)则AB:xm/R²+yn/R²=1且有a=4m/R²,b=n/R²得4m²+n²=R^4m²+n²=R²故|AB|²=(a-m)²+(b-n)²=R²+(16m²+n²)/R^4-...