title: iPad - Portrait and Landscape - Calculate how much angle it made with my desk
body: <p>I'm creating an app for iPad that works both in landscape and portrait mode.
  I want to place one edge of iPad on my desk and slant(angle) it.
  Now I want to measure how much angle it made with my desk. 
  Using accelerometer, I'm getting X,Y and Z values. But I couldn't find how to convert those values into degrees.
  Any way to convert XYZ to degrees?</p>