C语言中有关三角形面积的求解~~~

C语言中有关三角形面积的求解~~~

已知平面上三角形3个顶点坐标 x[3],y[3], 计算 3 角形面积：
#include
#include
double tri_area_2D(double x[3], double y[3]){
double a,b,c,s;
double dx1,dx2,dx3,dy1,dy2,dy3,dz1,dz2,dz3;
double area;
dx1 = x[1]-x[0]; dx2 = x[2]-x[1]; dx3 = x[0]-x[2];
dy1 = y[1]-y[0]; dy2 = y[2]-y[1]; dy3 = y[0]-y[2];
a = sqrt( dx1*dx1 + dy1*dy1 );
b = sqrt( dx2*dx2 + dy2*dy2 );
c = sqrt( dx3*dx3 + dy3*dy3 );
s = (a+b+c)/2.0;
area = sqrt(s * (s-a)*(s-b)*(s-c));
return area;
}
//已知空间三角形，3个顶点坐标 计算三角形面积：
double tri_area_3D(double x[3], double y[3], double z[3]){
double a,b,c,s;
double dx1,dx2,dx3,dy1,dy2,dy3,dz1,dz2,dz3;
double area;
dx1 = x[1]-x[0]; dx2 = x[2]-x[1]; dx3 = x[0]-x[2];
dy1 = y[1]-y[0]; dy2 = y[2]-y[1]; dy3 = y[0]-y[2];
dz1 = z[1]-z[0]; dz2 = z[2]-z[1]; dz3 = z[0]-z[2];
a = sqrt( dx1*dx1 + dy1*dy1 + dz1*dz1);
b = sqrt( dx2*dx2 + dy2*dy2 + dz2*dz2);
c = sqrt( dx3*dx3 + dy3*dy3 + dz3*dz3);
s = (a+b+c)/2.0;
area = sqrt(s * (s-a)*(s-b)*(s-c));
return area;
}

main( ){
double x[]={1,2,2},y[]={1,0,2},z[]={0,0,0};
printf("%lf ", tri_area_3D(x,y,z)); // 三维调用
printf("%lf ", tri_area_2D(x,y)); //二维调用
return 0;
}

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