Correcting the Gaussian Formula
diff --git a/maths/gaussian.py b/maths/gaussian.py
index 5d5800e00989..a5dba50a927d 100644
--- a/maths/gaussian.py
+++ b/maths/gaussian.py
@@ -1,9 +1,5 @@
 """
 Reference: https://en.wikipedia.org/wiki/Gaussian_function
-
-python/black : True
-python : 3.7.3
-
 """
 from numpy import exp, pi, sqrt
 
@@ -16,6 +12,12 @@ def gaussian(x, mu: float = 0.0, sigma: float = 1.0) -> int:
     >>> gaussian(24)
     3.342714441794458e-126
 
+    >>> gaussian(1, 4, 2)
+    0.06475879783294587
+
+    >>> gaussian(1, 5, 3)
+    0.05467002489199788
+
     Supports NumPy Arrays
     Use numpy.meshgrid with this to generate gaussian blur on images.
     >>> import numpy as np
@@ -49,8 +51,8 @@ def gaussian(x, mu: float = 0.0, sigma: float = 1.0) -> int:
 
     >>> gaussian(2523, mu=234234, sigma=3425)
     0.0
-  """
-    return 1 / sqrt(2 * pi * sigma ** 2) * exp(-((x - mu) ** 2) / 2 * sigma ** 2)
+    """
+    return 1 / sqrt(2 * pi * sigma ** 2) * exp(-((x - mu) ** 2) / (2 * sigma ** 2))
 
 
 if __name__ == "__main__":

I have added the parenthesis around the 2*sigma^2 term.

### **Describe your change:**



* [ ] Add an algorithm?
* [x] Fix a bug or typo in an existing algorithm?
* [ ] Documentation change?

### **Checklist:**
* [x] I have read [CONTRIBUTING.md](https://github.com/TheAlgorithms/Python/blob/master/CONTRIBUTING.md).
* [x] This pull request is all my own work -- I have not plagiarized.
* [x] I know that pull requests will not be merged if they fail the automated tests.
* [x] This PR only changes one algorithm file.  To ease review, please open separate PRs for separate algorithms.
* [x] All new Python files are placed inside an existing directory.
* [x] All filenames are in all lowercase characters with no spaces or dashes.
* [x] All functions and variable names follow Python naming conventions.
* [x] All function parameters and return values are annotated with Python [type hints](https://docs.python.org/3/library/typing.html).
* [x] All functions have [doctests](https://docs.python.org/3/library/doctest.html) that pass the automated testing.
* [x] All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
* [x] If this pull request resolves one or more open issues then the commit message contains `Fixes: #{$ISSUE_NO}`.
