# Functions

What is a function? How can you describe a function? What are the most important standard functions?

### What is a function?

What is a function? A function is a rule that relates two given sets: to each object of one set, it associates precisely one object from the other set.You will learn to see a mathematical function as a machine performing an operation on an input and learn about domain and codomain.

### Summary about functions - part 2

What are the properties of trigonometric functions: the sine, cosine and tangent? What is an exponential function and what is the inverse of the exponential function: the logarithm? This video gives the summary of week 2 of the edX course: pre-university Calculus (Calc001x)