Circle movement clockwise and counter clockwise

Hi. I got my object to move circle movement clockwise nicely with code:

Code (CSharp):

1. private float RotateSpeed = 1f;
2. private float Radius =4f;
3.  
4. private Vector2 _centre;
5. private float _angle;
6.  
7. private void Start()
8. {
9. _centre = transform.position;
10. }
11.  
12. private void Update()
13. {
14.  
15. _angle += RotateSpeed * Time.deltaTime;
16.  
17. var offset = new Vector2(Mathf.Sin(_angle), Mathf.Cos(_angle)) * Radius;
18. transform.position = _centre + offset;
19. }

But now I have problems to change it to move counter clockwise..What I should change?

 

Try

_angle -= RotateSpeed * Time.deltaTime;