Vector2Extension

using UnityEngine;

public static class Vector2Extension
{
    public static Vector2 GetDirectionAlongCircle(Vector2 targetPositioin, Vector2 selfPoisition, float speed)
    {
        Vector2 r = selfPoisition - targetPositioin;
        float angle = GetRotationAngle(r.magnitude, speed);
        Vector2 rotatedR = RotateVector(r, angle);
        return (rotatedR - r).normalized;

        float GetRotationAngle(float r, float chord) =>
            Mathf.Asin(chord / (2 * r)) * 2;
    }
    public static Vector2 RotateVector(Vector2 vector, float rad)
    {
        Vector2 right = new Vector2(Mathf.Cos(rad), Mathf.Sin(rad));
        Vector2 up = new Vector2(-Mathf.Sin(rad), Mathf.Cos(rad));
        return new Vector2(right.x * vector.x + up.x * vector.y,
                           right.y * vector.x + up.y * vector.y);
    }
}