diff --git a/mathgenerator/calculus.py b/mathgenerator/calculus.py
index 0455d7d..796ff1f 100644
--- a/mathgenerator/calculus.py
+++ b/mathgenerator/calculus.py
@@ -94,7 +94,7 @@ def stationary_points(max_exp=3, max_coef=10):
             problem += coefficient * pow(x, exp)
         solution = sympy.stationary_points(problem, x)
 
-    problem = 'f(x)=' + str(problem).replace('**', '^').replace('*','')
+    problem = 'f(x)=' + str(problem).replace('**', '^').replace('*', '')
     return f'${problem}$', f'${sympy.latex(solution)[6:-8]}}}$'
 
 
diff --git a/mathgenerator/geometry.py b/mathgenerator/geometry.py
index a36dee9..a68dd32 100644
--- a/mathgenerator/geometry.py
+++ b/mathgenerator/geometry.py
@@ -554,7 +554,7 @@ def volume_cone(max_radius=20, max_height=50, unit='m'):
 
 def volume_cube(max_side=20, unit='m'):
     """Volume of a cube
-    
+
     | Ex. Problem | Ex. Solution |
     | --- | --- |
     | Volume of a cube with a side length of $19m$ is | $6859 m^3$ |