title: Calculate the distance between two CGPoints
body: <p>i need to calculate the distance between two <code>CGPoint</code>s. I refered <a href="http://blog.digitalagua.com/2008/06/30/calculate-distance-between-two-points-in-objective-c/" rel="noreferrer">this</a> and <a href="https://stackoverflow.com/questions/1906511/how-to-find-the-distance-between-two-cg-points">this</a>, but I don't get it.</p>