Rotate object around world origin - matrix

Question

I am currently trying to rotate a positionVector (0,0,1) around the world's x-axis and then rotate it back to its original position (just trying to get it to work). I read into rotation matrixes and got it working (sorta) but i am pretty stuck now.
As the image and code shows i create a cube at the starting point (0,0,1) and rotate it down in this case 30 degrees. But it seems to rotate more than 30 degrees when rotating clockwise. However when i rotate it back counterclockwise (30 degrees) it does rotate the proper amount. Which results in it not ending up at its starting point as it should (0,0,1).
I was wondering if any of you could shed some light on why this is happening and how to fix it. Thank you guys in advance!
public float RotAngle = 330f;
public GameObject cube;
public GameObject original;
public GameObject relocator;
public GameObject initialTurn;
void Start ()
{
Vector3 pixelPos = new Vector3(0f, 0f, 1f);
original = GameObject.Instantiate(cube,pixelPos,Quaternion.identity) as GameObject;
original.name = "Original";
initialTurn = GameObject.Instantiate(cube, pixelPos, Quaternion.identity) as GameObject;
initialTurn.name = "InitialTurn";
relocator = GameObject.Instantiate(cube, pixelPos, Quaternion.identity) as GameObject;
relocator.name = "Relocator";
}
void Update()
{
initialTurn.transform.position = RotateAroundOrigin(original.transform.position, RotAngle*Mathf.Deg2Rad);
relocator.transform.position = RotateAroundOrigin(initialTurn.transform.position, (RotAngle * -1f) * Mathf.Deg2Rad);
}
Vector3 RotateAroundOrigin(Vector3 startPos,float angle)
{
startPos.Normalize();
startPos.y = (startPos.y * Mathf.Cos(angle)) - (startPos.z * Mathf.Sin(angle));
startPos.z = (startPos.y * Mathf.Sin(angle)) + (startPos.z * Mathf.Cos(angle));
return startPos.normalized;
}

Answer 1

You can rotate a direction vector pretty easily with a Quaternion.
Try this:
Vector3 RotateAroundOrigin(Vector3 startPos,float angle)
{
startPos.Normalize();
Quaternion rot = Quaternion.Euler(angle, 0.0f, 0.0f); // Rotate [angle] degrees about the x axis.
startPos = rot * startPos;
return startPos;
}