Unity : How to calculate the Area of Triangle in 3D?

TrinagleArea.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;


public class AreaOfTrinagle : EditorWindow
{
    string objectBaseName = "";
    int objectId = 1;
    GameObject objectToSpawn;
    float objectScale;
    float areaResult = 0f;

    Vector3 pointA;
    Vector3 pointB;
    Vector3 pointC;

    [MenuItem("Tools/AreaOfTrinagle")]
    public static void ShowWindow()
    {
        GetWindow(typeof(AreaOfTrinagle)); //GetWindow is a method inherited from the EditorWindow class
    }

    public void OnGUI()
    {
        GUILayout.Label("Spawn new Object", EditorStyles.boldLabel);

        //EditorGUILayout.FloatField("Spawn Radius", spawnRadius);
        pointA = EditorGUILayout.Vector3Field("A", pointA);
        pointB = EditorGUILayout.Vector3Field("B", pointB);
        pointC = EditorGUILayout.Vector3Field("C", pointC);

        //https://math.stackexchange.com/questions/128991/how-to-calculate-the-area-of-a-3d-triangle
        areaResult = EditorGUILayout.FloatField("Area : ", CalculateAreaOfTrinagle(pointA, pointB, pointC));
    }


    float CalculateAreaOfTrinagle(Vector3 n1, Vector3 n2 , Vector3 n3)
    {
        float res  = Mathf.Pow(((n2.x * n1.y) - (n3.x * n1.y) - (n1.x * n2.y) + (n3.x * n2.y) + (n1.x * n3.y) - (n2.x * n3.y)), 2.0f);
              res += Mathf.Pow(((n2.x * n1.z) - (n3.x * n1.z) - (n1.x * n2.z) + (n3.x * n2.z) + (n1.x * n3.z) - (n2.x * n3.z)), 2.0f);
              res += Mathf.Pow(((n2.y * n1.z) - (n3.y * n1.z) - (n1.y * n2.z) + (n3.y * n2.z) + (n1.y * n3.z) - (n2.y * n3.z)), 2.0f);
        return Mathf.Sqrt(res) * 0.5f;
    }

    private void CalculateTheArea()
    {
        
    }

}