What are some examples of bounded functions?

1 Answer
Oct 21, 2015

sin(x)sin(x), cos(x)cos(x), arctan(x)=tan^{-1}(x)arctan(x)=tan1(x), 1/(1+x^2)11+x2, and 1/(1+e^(x))11+ex are all commonly used examples of bounded functions.

Explanation:

A function f(x)f(x) is bounded if there are numbers mm and MM such that m leq f(x) leq Mmf(x)M for all xx. In other words, there are horizontal lines the graph of y=f(x)y=f(x) never gets above or below.

sin(x)sin(x), cos(x)cos(x), arctan(x)=tan^{-1}(x)arctan(x)=tan1(x), 1/(1+x^2)11+x2, and 1/(1+e^(x))11+ex are all commonly used examples of bounded functions (as well as being defined for all x in RR). There are plenty more examples that can be created.

The graph of 1/(1+e^(x)) is interesting because it has two distinct horizontal asymptotes (arctan(x) does too). The graph of 1/(1+e^(x)) is shown below.

graph{1/(1+e^(x)) [-5, 5, -2.5, 2.5]}