**Function (mathematics) - Wikipedia**
https://en.wikipedia.org/wiki/Function_(mathematics)

Several methods for specifying functions of real or complex variables start from a local definition of the function at a point or on a neighbourhood of a point, and then extend by continuity the function to a much larger domain. Frequently, for a starting point $${\displaystyle x_{0},}$$ there are several possible starting values for the function. For example, in defining the square root as the inverse function of the square function, for any positive real number $${\displaystyle x_{0},}$$ there are two choices for the value of t…

**DA:** 63 **PA:** 38 **MOZ Rank:** 58