title: Sympy computing the inverse laplace transform
body: <p>I am having some trouble computing the inverse laplace transform of a symbolic expression using sympy. In matlab and in the book I am working from the expression s/(s^2 + w^2) transforms to cos(wt).</p>
  
  <p>When I attempt to do this using sympy like so:</p>
  
  <pre><code>expression = s/(s**2+w**2)
  Answer = sympy.inverse_laplace_transform(expression, s, t)
  </code></pre>
  
  <p>I get that</p>
  
  <pre><code>Answer = (-I*exp(2*t*im(w))*sin(t*re(w)) + exp(2*t*im(w))*cos(t*re(w)) + I*sin(t*re(w)) + cos(t*re(w)))*exp(-t*im(w))*Heaviside(t)/2
  </code></pre>
  
  <p>What am I doing wrong?</p>