Rotating spot light

Hi,

I want to rotate a spot light arount Y Axis. I have written the followin script and attached it to the spot light: using UnityEngine; using System.Collections;

     public class RotateSpot : MonoBehaviour {
         public float rotateSpeed = 10f;
         float xangle;
          float zangle;
        // Use this for initialization
       void Start () {
           float xangle = transform.rotation.x;
           float zangle = transform.rotation.z;
        }
 
 // Update is called once per frame
        void Update () {
            transform.Rotate(new Vector3(xangle, Time.deltaTime*rotateSpeed, zangle));
       }
   }

But the spot does not rotate, more it disappears. How to improve the script ?

Thank you.