Finding z-axis angle using Mathf.atan2

Hello,

I'm trying to calculate the angle between two vectors and apply to the z rotation of an object. I'm using atan2 for that.

But something seems to be wrong, why should an angle between vector.up and vector.right be 45 degrees (and not 90)? Take a look at this:

         Vector3 upVec = Vector3.up;
         Vector3 rightVec = Vector3.right;
         
         float deltaY = rightVec.y - upVec.y;
         float deltaX = rightVec.x - upVec.x;
         
         float angle = Mathf.Atan2(deltaY, deltaX) * Mathf.Rad2Deg;
         
         Debug.Log("angle " + angle);