title: Sympy returns log instead of ln
body: <p>I have this equation:</p>
  
  <pre class="lang-py prettyprint-override"><code>import sympy as sp
  
  x = sp.Symbol(‘x’, real = True)
  fx = sp.log(x,3)
  
  sp.diff(fx, x) 
  </code></pre>
  
  <p><strong>Sympy returns:</strong></p>
  
  <pre><code>1/(x*log(3))
  </code></pre>
  
  <p><strong>Sympy should return:</strong></p>
  
  <pre><code>1/(x*ln(3))
  </code></pre>
  
  <p>Why is Sympy returning the log function rather than the natural log function?</p>