I'm making a 3D camera scene in Flash, draw using drawTriangles() and rotated and translated using a Matrix3D. I've got the camera to look after a specific point, but only on the Y-axis, using the x and z coordinates, here is my code so far:

var dx:Number = camera.x - lookAt.x;
var dy:Number = camera.y - lookAt.y;
var dz:Number = camera.z - lookAt.z;

camera.rotationY = Math.atan2(dz, dx) * (180 / Math.PI) + 270;

so no matter the x or z position, the point is always on the mid of the screen, IF and only if y matches with the camera. So what I need is to calculate the rotationX (which are measured in degrees not radians), and I was wondering how I would do this?