判断点P是否在ABC内

给定三角形ABC和一点P(x,y,z)，判断点P是否在ABC内，给出思路并手写代码

#include<iostream>
#include<algorithm>

#define ABS_FLOAT_0 0.0001

using namespace std;

// 求三角形的面积
// 根据向量求三角形的面积
double funAreaTriAngle(double dAx, double dAy, double dBx, double dBy, double dCx, double dCy)
{
	double dABx = dBx - dAx;
	double dABy = dBy - dAy;
	double dACx = dCx - dAx;
	double dACy = dCy - dAy;

	return abs(dABx*dACy - dABy*dACx) / 2.0;

}

// 判断P点是否在三角形ABC中
// 通过ABC，ABP，ACP,BCP的面积判断
bool funTriMid(double dAx, double dAy, double dBx, double dBy, double dCx, double dCy, double dPx, double dPy)
{
	double dAreaABC= funAreaTriAngle(dAx, dAy, dBx, dBy, dCx, dCy);

	double dAreaABP = funAreaTriAngle(dAx, dAy, dBx, dBy, dPx, dPy);
	double dAreaAPC = funAreaTriAngle(dAx, dAy, dPx, dPy, dCx, dCy);
	double dAreaPBC = funAreaTriAngle(dPx, dPy, dBx, dBy, dCx, dCy);

	if (abs(dAreaABC - (dAreaABP + dAreaAPC + dAreaPBC)) < ABS_FLOAT_0){
		return true;
	}
	return false;
}


int main