# How to Graph X in Terms of Y on a TI-84 Calculator

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The TI-84 calculator offers a number of built-in functions to solve and graph equations. Unfortunately, its core graphing options are limited to functions and equations that feature Y in terms of X. It's less common that you'll need to graph X in terms of Y, but if you do then the existing options won't quite cut it. Fortunately, the TI-84 allows you to import external apps and use them in much the same way as you would use the apps that ship with the calculator. The community-supported TI Calc repository contains a number of these external apps, including an app called XGraph by Joel Smith that lets you graph X in terms of Y.

## What Does X in Terms of Y Mean?

For most equations, you graph Y in terms of X. What this means is that your equation is based on the value of Y, and it's interpreted through the value of X; an example of this would be y = x + 1. The value of Y depends on what the value of X is, so for each X the corresponding Y value is equal to that X value plus 1. Graphing X in terms of Y turns this around. Instead of y = x + 1, you would create a graph out of x = y + 1. In this case, your X value is dependent on the value of Y and to calculate each X you take its corresponding Y value and add 1. Unfortunately, this isn't easy to graph on a TI-84 calculator unless you calculate and plot individual points by hand since the TI-84 doesn't have an "X=" option in its graphing functions.

## Using the App

Press the PRGM button on your TI-84 calculator and locate the "XGRAPH" entry in your program list. Press the ENTER key, causing "prgmXGRAPH" to appear on your screen; press ENTER again to launch the app. When prompted, enter your equation but use the letter X instead of Y. If you were hoping to graph an equation such as x = 2y + 1, your XGraph input would be "X=? 2X + 1" instead. Press the ENTER key and wait while the program draws the graph; despite entering X in your input, the graph will be drawn as X in terms of Y (which for the example above would be the graph of x = 2y + 1.) Once you've finished, press the ON button to break the program and select "1:Quit" to exit.

#### About the Author

Holding a BS in computer science and several years of experience building, repairing and maintaining computers and electronics, Jack Gerard has had a love of science and mathematics for years. When not working on writing projects as part of his 15+ year career, he also works as a programmer writing gaming and accessibility software.

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