Question How to make Mathf.Sin always start at the point?

Hi, Quick question. How do I make Mathf.Sin always start from the same point?

So quick explanation of usage:
I have a 2D character. When the mouse clicks, the characters arm rotates up and down. My current implementation works but the problem is that when the mouse is clicked, the rotation starts at a different point everytime, Where as I would really like it to start at the "mid point", preferably when rotating upwards.

Here is a snippet of the current implementation:

Code (CSharp):

1.  
2. private void Update()
3. {
4.     float swingSpeed = 15f;
5.     float maxRotation = 60f;
6.  
7.     float rot = maxRotation * Mathf.Sin(Time.time * swingSpeed) + Mathf.Atan2(lookDir.y, lookDir.x) * Mathf.Rad2Deg + 45f;
8.  
9.     weaponArm.transform.rotation = Quaternion.Euler(0f, 0f, rot);
10. }
11.  

Any help would be great. Thanks.

 

Code (CSharp):

1.     private void Update()
2.     {
3.         float swingSpeed = 15f;
4.         float maxRotation = 60f;
5.         float rot = maxRotation * Mathf.Cos(swingTime * swingSpeed) + Mathf.Atan2(lookDir.y, lookDir.x) * Mathf.Rad2Deg + 45f;
6.         weaponArm.transform.rotation = Quaternion.Euler(0f, 0f, rot);
7.         swingTime+=Time.deltaTime; // reset swingTime to zero when mouse is clicked
8.     }

 

Ah wonderful. That did it.

Thank you!