title: problem with implicit plots with absolute functions
body: <p>I'm transcribing code from Mathematica to Python (I'm using spyder). However, when plotting the graph, I can't get the plot looking like this:</p>
  
  <p><img src="https://i.stack.imgur.com/tVBvB.png" alt="desired plot"></p>
  
  <p>The code produces:</p>
  
  <p><img src="https://i.stack.imgur.com/1NAKd.png" alt="plot from the code"></p>
  
  <pre><code>import numpy as np
  import sympy as sym
  
  
  nc=1.772
  c=3e10
  L=0.3
  R=3.0
  lbd=775e-7
  d = sym.Symbol ('d')
  rep = sym.Symbol ('rep')
  
  M1=np.array([[1,(L/2)],[0,1]]) #espessura_cristal
  
  M2=np.array([[1,0],[0,(1/nc)]]) #ar_cristal 
  
  M3=sym.Matrix ([[1,(d/2)-L/2],[0,1]]) #dis_cristal_esp
  #print M3
  M4=np.array([[1,0],[(-2/R),1]]) #espelho 
  
  M5= sym.Matrix ([[1,(c/rep)-d],[0,1]]) #comp_cavidade
  #print M5
  M6=np.array([[1,0],[0,nc]]) #cristal_ar 
  
  
  M = sym.Matrix(M1*M2*M3*M4*M5*M4*M3*M6*M1)
  
  est = sym.Eq(((M[0,0]+M[1,1])**2),4.0)
  
  sol=sym.solve(est)
  print sol
  
  sym.plot_implicit(est,(rep,0.1,1),(d,1,10))
  </code></pre>
  
  <p>What am I doing wrong?</p>