Is this a function

Question

Body temperature depends on the time of day is this a function

Answer 1

A function has independent variable(s) that may change at any time for any reason.  Time of day is an independent variable.

 

A function has a dependent variable that varies based on the value of the independent variable(s).  Body temperature changes as the day progresses (although the time of day may not predict body temperature, there is only one body temperature at a given time of day).

 

The "vertical line test" means that a function has either exactly one or no value of the dependent variable for each value of the independent variable.  Yes, body temperature has one value for each time of day on each date that we consider.

 

It is a function.

 

Note:  there may be multiple times of the day when there is the same body temperature;  thus, time of day is not a function of body temperature.