title: Fill a drawn triangle using lines
body: <p>i need to generate a new method to fill the triangle in the below code and call it separately
  any advise please?</p>
  
  <pre><code>public void draw(Graphics g, Pen blackPen)
      {
          double xDiff, yDiff, xMid, yMid;
  
          xDiff = oppPt.X - keyPt.X;
          yDiff = oppPt.Y - keyPt.Y;
          xMid = (oppPt.X + keyPt.X) / 2;
          yMid = (oppPt.Y + keyPt.Y) / 2;
  
          // draw triangle
          g.DrawLine(blackPen, (int)keyPt.X, (int)keyPt.Y, (int)(xMid + yDiff / 2), (int)(yMid - xDiff / 2));
          g.DrawLine(blackPen, (int)(xMid + yDiff / 2), (int)(yMid - xDiff / 2), (int)oppPt.X, (int)oppPt.Y);
          g.DrawLine(blackPen, (int)keyPt.X, (int)keyPt.Y, oppPt.X, oppPt.Y);
  
      }
  </code></pre>
  
  <p>the method should take both of these arguments</p>
  
  <pre><code>public void fillTriangle(Graphics g, Brush redBrush)
      {
  
  
      }
  </code></pre>