title: Custom animation: easing out
body: <p>I have successfully created a custom animation in a drawing in a <code>UIView</code> by using a repeating <code>Timer</code> to increment the alpha of the drawing every few milliseconds.</p>
  
  <p>Now, I want to achieve an easing out animation (deceleration) with my drawing. I would like to do this by firing a new timer with a longer interval every time the <code>Timer</code> is called, so that the alpha increments slower, resulting in deceleration. </p>
  
  <p>I know that there is an easeOut animation from <code>CAMediaTiming</code>, but I would like to know if there is any built in function to get the decelerating numbers. For example, if I pass in a constant of 10, every time I call the function I can get decelerating numbers like 15, 18, 20, 21, 21.5, etc.</p>