tangent vectors for circle equation points

Unity Engine
1

i’m trying to get the tangent vector for each point on the circle , i tried to use the derivative for the circle equation, but the result looks off in the viewport, so i’m wondering if i can find some help here

the code

    public void OnDrawGizmos(){
        step = (360.0f * Mathf.Deg2Rad) / numberOfPoints ;
        CreateVertices();
    }

void CreateVertices()
{

    Points.Clear();
    Normals.Clear();
    Tangents.Clear();

    float dynamicAngle = 0.0f;
    for (int i = 0; i <= numberOfPoints; i++)
    {
        Vector3 point;
        point.x = transform.position.x + Radius * Mathf.Cos(dynamicAngle);
        point.y = transform.position.y + Radius * Mathf.Sin(dynamicAngle);
        point.z = transform.position.z;


        dynamicAngle = dynamicAngle + step;
        if (i >= 1)
        {
            Gizmos.color = Color.red;
            Gizmos.DrawLine(Points[i - 1], point);
            Gizmos.color = Color.white;
        }
        Points.Add(point);
        CalculateNormals(dynamicAngle ,point);
        CalculateTangents(dynamicAngle ,i , point);

    }

}

void CalculateNormals(float dynamicAngle , Vector3 point)
{
    Vector3 Normal = (point - transform.position).normalized;

    Gizmos.color = Color.magenta;
    Gizmos.DrawLine(Normal, point);
    Gizmos.color = Color.white;

    Normals.Add(Normal);

}

void CalculateTangents(float dynamicAngle,int i ,Vector3 point)
{
    Vector3 tangent;
     tangent = new Vector3(-Normals[i].y, Normals[i].x, 0);
     tangent.Normalize();

    Gizmos.color = Color.blue;
    Gizmos.DrawLine(  point, tangent);
    Gizmos.color = Color.white;

    Tangents.Add(tangent);
}

Blue is the tangents purple is the normals, as you can see they are not perpendicular

1128×681 134 KB

2

little update
ive changed the code took the derivative off and used this instead

  tangent = new Vector3(-Normals[i].y, Normals[i].x, 0);

, it looks much more correct now but only when the radius is close to 0
can anyone give me a little explanation on why this is happening