problem with angles
<p>Hi
this a part of my code :
I have a list which its size is three and I consider that 2 last items are in one line (p and q) I need to get the angle between the first item of this list and these two points (p,q)</p>

<pre><code>    private Point partition(List&lt;Point&gt; list, Point p, Point q) {



    double x1 = p.getX();
    double x2 = q.getX();
    double y1 = p.getY();
    double y2 = q.getY();
    double pQ = Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1));
    for (int i = 0; i &lt; list.size()-2; i++) {
        double pointX = list.get(i).getX();
        double pointY = list.get(i).getY();
        double pointQ = Math.sqrt((x2 - pointX) * (x2 - pointX) + (y2 - pointY) * (y2 - pointY));
        double pointP = Math.sqrt((pointX - x1) * (pointX - x1) + (pointY - y1) * (pointY - y1));
        double angle = Math.acos((pQ * pQ - pointP * pointP - pointQ * pointQ) /(- 2 * pointP * pointQ));
        System.out.println(angle);


    }
</code></pre>

<p>but instead of printing an angle for the first item it will print :(first item is not in the line of two last items).</p>

<pre><code>1.6288442476732894
</code></pre>

<p>those points that print  this result are :</p>

<pre><code>[X :143.0  Y: 217.0, X :93.0  Y: 163.0, X :193.0  Y: 165.0]
</code></pre>

<p>please help me thanks.</p>

<p>EDITED : really it makes me confused .in such a way it will print this value ,sorry all !!!</p>
