Question

已知三点求圆的方程的c语言编程

Answer 1

/***************
* 已知三点求圆的 get_circle() 函数
* x1, y1为第一个点的坐标，以此类推
* r为求出的半径，x0, y0为圆心坐标
* 调用函数之前应先检查三点是否共线 否则会弹出被零除的错误
***************/
# include <math.h>
void get_circle(double x1, double y1, double x2, double y2, double x3, double y3, double* r, double* x0, double* y0)
{
double m1, n1, m2, n2, a1, b1, a2, b2;
m1 = (x1 + x3) / 2;
n1 = (y1 + y3) / 2;
m2 = (x2 + x3) / 2;
n2 = (y2 + y3) / 2;
a1 = (y3 - y1) / (x3 - x1);
b1 = n1 - a1*m1;
a2 = (y3 - y2) / (x3 - x2);
b2 = n2 - a2*m2;
*x0 = (b2 - b1) / (a1 - a2);
*y0 = a1 * *x0 + b1;
*r = sqrt((x1-x0)*(x1-x0) + (y1-y0)*(y1-y0));
return;
}

希望对你有帮助！

Answer 2

/*相关子函数由一楼abccsss的代码修改而成，其中第一个和第二个点以及第二个和第三个点的连线不得经过圆心！第一个和第二个点以及第二个和第三个点的横纵坐标不得相同！*/
#include<stdio.h>
# include <math.h>
void get_circle(double x1, double y1, double x2, double y2, double x3, double y3, double* r, double* x0, double* y0)
{
double m1, n1, m2, n2, a1, b1, a2, b2;
m1 = (x1 + x2) / 2;
n1 = (y1 + y2) / 2;
printf("\n\t第一条垂直平分线必过点为(%f,%f)",m1,n1);
m2 = (x2 + x3) / 2;
n2 = (y2 + y3) / 2;
printf("\n\t第二条垂直平分线必过点为(%f,%f)",m2,n2);
a1 = -(x2 - x1)/(y2 - y1);
b1 = n1 - a1*m1;
printf("\n\t第一条垂直平分线为y=%fx+%f",a1,b1);
a2 = -(x3 - x2)/(y3 - y2);
b2 = n2 - a2*m2;
printf("\n\t第二条垂直平分线为y=%fx+%f",a2,b2);
*x0 = (b2 - b1) / (a1 - a2);
*y0 = a1 * *x0 + b1;
*r = sqrt((x1-*x0)*(x1-*x0) + (y1-*y0)*(y1-*y0));
return;
}
typedef struct{
float x;
float y;
}bit;
main(){
printf("\n\t\t\t输入三个点以计算圆心和半径");
bit d[3];
printf("\n\t输入第一个点的坐标：");
scanf("%f,%f",&d[0].x,&d[0].y);
printf("\n\t输入第二个点的坐标：");
scanf("%f,%f",&d[1].x,&d[1].y);
printf("\n\t输入第三个点的坐标：");
scanf("%f,%f",&d[2].x,&d[2].y);
double r,x0,y0;
get_circle(d[0].x,d[0].y,d[1].x,d[1].y,d[2].x,d[2].y,&r,&x0,&y0);
printf("\n\t\t圆心为：（%f,%f）,半径为%f",x0,y0,r);
}

Answer 3

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