How to calculate angle in the triangle formed by screen touches

Question

I am trying to calculate the angles of a triangle that is formed by three touches on the screen (1,2,3) - please look at the attached picture and the angles marked in red. I am using Vector2.Angle for this but I am not sure if I am doing it correctly. Can you suggest how to do it so that every new touch on the screen when such a triangle is formed, I check every angle ?

 public class TouchPosition : MonoBehaviour
 {
     public Text distanceText, angleText;
     public float angle, distance;
     void Update()
     {
         CheckDistanceAndAngle();
     }
 public void CheckDistanceAndAngle()
     {
         for (int i = 2; i < Input.touchCount; i++)
         {
             for (int j = 0; j < i; j++)
             {
                 distance = Vector2.Distance(Input.touches[i].position, Input.touches[j].position);
                 angle = Vector2.Angle(Input.touches[j].position, Input.touches[j].position - 
                 Input.touches[i].position);
                 Debug.Log($"i: {i}");
                 Debug.Log($"j: {j}");
                 Debug.Log($"Touch {i} position: {Input.touches[i].position}");
                 Debug.Log($"Touch {j} position: {Input.touches[j].position}");
 
                 distanceText.text = " Distance : " + distance;
                 angleText.text = "Angle : " + angle;
             }
         }
     }
 }

alt text

Answer 1

Code not tested

 float[] angles = new float[3];
 public void CheckDistanceAndAngle()
 {
     int touchCount = Input.touchCount;
     int i = 0;
     for (; touchCount > 2 && i < touchCount && i < angles.Length; i++)
     {
         Vector2 vertex = Input.GetTouch(i).position;
         Vector2 previous = Input.GetTouch((i - 1 + touchCount) % touchCount).position;
         Vector2 next = Input.GetTouch((i + 1) % touchCount).position;
         angles[i] = Vector2.Angle(previous - vertex, next - vertex);
     }
     for (; i < angles.Length; i++)
     {
         angles[i] = 0;
     }
     angleText.text = $"Angles: [{string.Join(",", angles)}]";
 }

For all possible combinations of triangles with the touches

(Code tested)

 public void CheckDistanceAndAngle()
 {
     int touchCount = Input.touchCount;

     if(touchCount <= 2)
         return;

     System.Text.StringBuilder stringBuilder = new System.Text.StringBuilder("Angles:");

     for (int firstTouchIndex = 0; firstTouchIndex < touchCount; firstTouchIndex++)
     {
         for (int secondTouchIndex = firstTouchIndex + 1; secondTouchIndex < firstTouchIndex + touchCount - 1; secondTouchIndex++)
         {
             for (int thirdTouchIndex = secondTouchIndex + 1; thirdTouchIndex <= firstTouchIndex + touchCount - 1; thirdTouchIndex++)
             {
                 Vector2 first = Input.GetTouch(firstTouchIndex).position;
                 Vector2 second = Input.GetTouch(secondTouchIndex % touchCount).position;
                 Vector2 third = Input.GetTouch(thirdTouchIndex % touchCount).position;
                 float angle = Vector2.Angle(second - first, third - first);
                 stringBuilder.Append($"\n({firstTouchIndex + 1}, {(secondTouchIndex % touchCount) + 1}, {(thirdTouchIndex % touchCount) + 1}) = {angle}");
             }
         }
     }
     
     angleText.text = stringBuilder.ToString();
 }

How to calculate angle in the triangle formed by screen touches

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Code not tested

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