title: Given a vector, calculate a point at distance l
body: <p>This is an extraordinarily simple question but I can't find the answer so I'm bracing myself for the ridicule.</p>
  
  <p>Given a vector: 
  <img src="https://i.stack.imgur.com/fpya3.jpg" alt="enter image description here"></p>
  
  <p>(in this case going from 2,3 to 9,9) I want to start at 2,3 and travel up the vector a distance of length l.</p>
  
  <p>How do I calculate the new point (x,y)? Thanks!</p>
  
  <p>Here's the code (after implementing Dmitry's equation):</p>
  
  <pre><code> double MetersMoved = ((Dinosaurs[i].Speed * 1000) / (60 * 60)) * TimeStepInSecs;
   double fi = Math.Atan2((Dinosaurs[i].Goal.Y - Dinosaurs[i].Head.Y),(Dinosaurs[i].Goal.X - Dinosaurs[i].Head.X));
   Dinosaurs[i].Head.X = Dinosaurs[i].Head.X + MetersMoved * Math.Cos(fi);
   Dinosaurs[i].Head.Y = Dinosaurs[i].Head.Y + MetersMoved * Math.Sin(fi);
  </code></pre>
  
  <p>The dinosaurs are aligning themselves on the correct vector but not advancing (one should be moving 2 pixels and the other about 7). </p>
  
  <p>Dmitry's answer is correct.</p>