title: How to resolve 'ImmutableDenseNDimArray' object has no attribute 'could_extract_minus_sign'?
body: <p>First of all, I am new to coding.</p>
  
  <p>I am trying to simulate source flow in Python. But I am getting an error. How can I resolve it? Here's my code and error:</p>
  
  <p><strong>Code</strong></p>
  
  <pre><code>import numpy as nm
  from matplotlib import pyplot
  from sympy import *
  import math as math
  X,Y=symbols('X Y')
  N=50
  x_start,x_end=-2,2
  y_start,y_end=-1,1
  x=nm.linspace(x_start,x_end,N)
  y=nm.linspace(y_start,y_end,N)
  X,Y=nm.meshgrid(x,y)
  width=10.0
  height=width*((y_end-y_start)/(x_end-x_start))
  pyplot.figure(figsize=(width,height))
  pyplot.xlabel("X")
  pyplot.ylabel("Y")
  strength_source=10
  x_source,y_source=-0.5,-0.25
  q=(Y - y_source)/(X - x_source)
  u_source = (strength_source / (2 * math.pi) * diff(atan(q),Y))
  v_source = (strength_source / (2 * math.pi) * diff(atan(q),X))
  pyplot.scatter(x_source,y_source)
  pyplot.streamplot(X,Y,u_source,v_source,density=1, linewidth=1,
  arrowsize=2, arrowstyle='-&gt;')
  </code></pre>
  
  <p><strong>Error:</strong></p>
  
  <pre class="lang-none prettyprint-override"><code>  File "F:\Anaconda\lib\site-packages\sympy\functions\elementary\trigonometric.py", line 2298, in eval
      if arg.could_extract_minus_sign():
  
  AttributeError: 'ImmutableDenseNDimArray' object has no attribute 'could_extract_minus_sign'
  </code></pre>