The mathematics functions can be divided into these categories:

  • Linear Functions
  • Polynomials
  • Power Functions
  • Rational Functions
  • Algebraic Functions
  • Trigonometric Functions
  • Exponential Functions
  • Logarithmic Functions
  • Transcendental Functions

Where the most interesting category is the Rational Functions, of which a rational function is a ratio of two polynomials:


where P and Q are polynomials. The domain consists of all values of x such that image.

The interesting thing about the Rational Functions is that the graphs of some of them look like a human face! mostly the sad face.

The function

Sad face

is a rational function with domainimage. Its graph is shown as below.

Sad face

What is more, the graph of the below function


looks like the Chinese character “冏”:


Funny! Isn’t it?