title: Trying to solve for B in that equation
body: <p>I am trying to solve for the variable B in that long expression. It is giving me an error that it cannot convert to float. I am not really sure what that exactly means and what I need to do in order to fix that and get a value for B. I am very new to Python so any help would be appreciated.</p>
  
  <p>Code: </p>
  
  <pre><code>import matplotlib.pyplot as plt
  import numpy as np
  import math
  from sympy.solvers import solve
  from sympy import Symbol 
  
  W = 1*(10**(-4)) 
  mu = 300  
  Cox = 6.906*(10**-6)
  Leff = 1*(10**(-4))
  Vg1 = 0.5
  Vg2 = 1.0
  Vg3 = 1.5
  Vg4 = 2.0
  Vth = 0.0259
  tsi = 5 * (10 ** -7)
  Vg = [0.5, 1, 1.5, 2]
  Esi = 11.7
  tox = 1.5 * (10 ** -7)
  tsi = 5 * (10 ** -7)
  ni = 1.5 * (10 ** 10)
  q = 1.602 * (10 ** -19)
  
  B = Symbol('B')
  
  solve((Vg1/2*Vth) - math.log((2/tsi)*(np.sqrt((2*Esi*Vth)/(ni * q)))) - 
  math.log(B) + math.log(np.cos(B)) - 2*11.7*(tox)/(3.9 * tsi), B)
  </code></pre>
  
  <p>Error: </p>
  
  <pre><code>TypeError                                 Traceback (most recent call last)
  &lt;ipython-input-3-003cda8dedbd&gt; in &lt;module&gt;()
   18 B = Symbol('B')
   19 
   ---&gt; 20 solve((Vg1/2*Vth) - math.log((2/tsi)*(math.sqrt((2*Esi*Vth)/(ni * 
    q)))) - math.log(B) + math.log(math.cos(B)) - 2*11.7*(tox)/(3.9 * tsi), B)
  
  ~\Anaconda3\lib\site-packages\sympy\core\expr.py in __float__(self)
  237         if result.is_number and result.as_real_imag()[1]:
  238             raise TypeError("can't convert complex to float")
   --&gt; 239         raise TypeError("can't convert expression to float")
  240 
  241     def __complex__(self):
  
  TypeError: can't convert expression to float
  </code></pre>