# How to find domain and range on graphing calculator?May 8, 2008 8:37 PM   Subscribe

How (if possible) can you find the domain and range of a graph on a graphing calculator (which in my case is a TI-84 Plus)?
posted by meta.mark to Education (3 answers total)

Strictly speaking, the domain and range of the graph are defined by you using the "window" function. If you want the domain and range of the function, I think you'll have to do it the old fashioned way (by hand) or by using something that can manipulate symbols for you (e.g. a TI-89).

What, precisely, are you trying to do here?
posted by Commander Rachek at 9:05 PM on May 8, 2008

The domain is whatever you define it to be; that is, you could say f(x)=x² with x an integer only: you need to specify the domain when giving a function. Typically (at least in introductory math courses) it is assumed that the domain of a function f(x) is all real numbers x for which f(x) is a real number. Typically given that assumption, you need to find out the domain yourself: if there's a radical of even power and you're not involving complex numbers, you need to solve for when the radicand is negative; if there's a rational function, you need to solve for when the denominator is zero; if there's a tangent, cotangent, secant, or cosecant function, you need to solve for its undefined values; if there's a logarithmic function, you need to solve for when its argument is negative.
Finding the range (given a domain, of course) is not necessarily a straightforward process. Your best bet will be to look at the graph, as Commander Rachek suggested.
posted by likedoomsday at 10:13 PM on May 8, 2008

You don't need a calculator to find the domain/range of a function, nor should you be using one to try to find these things.