直线与椭圆相交求交点

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引自……CSDN

已知a,b和直线上的两点，中心在原点，求直线与椭圆相交求交点坐标

#include<stdio.h>#include<conio.h>#include<math.h>void main(){    double a,b,c,x1,x2,y1,y2,k,j;        printf("\nplease input a,b:\n");    scanf("%lf%lf",&a,&b);    printf("\nplease input x1,y1,x2,y2\n");    scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);    k=(y1-y2)/(x1-x2);    c=y1-k*x1;    j=(2*a*a*k*c)*(2*a*a*k*c)-4*(b*b+a*a*k*k)*a*a*(c*c-b*b);        if(j<0)        printf("\nthe line don't intersect with the ellipse");    else         if(j==0)        {            x1=-2*k*c*a*a/(2*(b*b+a*a*k*k));            y1=k*x1+c;            printf("\nthe line and ellipse intersect at\n(%lf,%lf)",x1,y1);        }    else    {        x1=(-2*k*c*a*a+sqrt(j))/(2*(b*b+a*a*k*k));        y1=k*x1+c;        x2=(-2*k*c*a*a-sqrt(j))/(2*(b*b+a*a*k*k));        y2=k*x2+c;        printf("\nthe line and ellipse intersect at\n(%lf,%lf) and (%lf,%lf)",x1,y1,x2,y2);    }        getch();}