title: Determine tangent based on initial tangent and curvature
body: <p>I'm having the following scenario : </p>
  
  <ul>
  <li>2 points, A and B are on a circle</li>
  <li>curvature of the circle, <strong><em>c</em></strong> (and hence its <strong><em>radius</em></strong> = 1/<strong><em>c</em></strong>) is known</li>
  <li>the tangent to the circle at point A, <strong><em>mA</em></strong> is known.</li>
  <li>the direct distance from A to B, <strong><em>dAB</em></strong> is known</li>
  <li>the arc distance <strong>dAB_arc</strong> is known</li>
  <li>the sector angle between A and B, <strong><em>theta</em></strong> is known</li>
  </ul>
  
  <p>I'm trying to deduct the tangent at point B, <strong><em>mB</em></strong>. Could anyone please help out ? 
  Thanks in advance.</p>