title: Drawing line from fixed point 50px towards mouse position Java
body: <p>I am trying to draw a line which is 50px in length from a fixed point to a point based on the position of the mouse but I am terrible at trigonometry. 
  I have been stuck on this all day and still have no idea how to do it.
  the four variables used are:</p>
  
  <pre><code>startX; //X position of fixed point
  startY; //Y position of fixed point
  mouseX; //X position of mouse
  mouseY; //Y position of mouse
  </code></pre>
  
  <p>Thanks in advance.</p>