##### Rutgers/Lucent ALLIES IN TEACHING MATHEMATICS AND TECHNOLOGY Grant

*Using technology not simply to do things better, but to do better things.*

__EXPLORING THE TI-83 GRAPHING CALCULATOR__

*Converting Celsius Temperatures to Fahrenheit*

To convert a temperature from degrees Celsius (*C *) to degrees Fahrenheit (*F *), we use the formula

*F * = (9⁄5)*C * + 32.

Outside of the United States, temperature readings are usually given in degrees Celsius. A rough approximation of the Fahrenheit equivalent for a Celsius reading can be found by doubling the Celsius reading and adding 32°.

- Write a formula to calculate the Fahrenheit approximation,
*F *, of a Celsius temperature, *C *.

- For what range of Fahrenheit temperatures, if any, is the approximation less than (or greater than) the correctly calculated value?

- For what temperature, if any, is the approximation the same as the correctly calculated temperature?

You can use the graphing calculator to help answer the questions.
- First create the algebraic equivalent of the approximation by "doubling and adding 32".

- Let "
**x**" represent the Celsius temperature (the independent variable), and "**y**" represent the Fahrenheit temperature (the dependent variable). Enter the correct equation in for "**Y**_{1}", and enter the approximation equation in as "**Y**_{2}".

- Determine and enter appropriate values for the Window settings. Look at the graph to insure you are seeing enough of the important information in the graph.

- You can use the TRACE function to approximate the relative values of "
**Y**_{1}" and "**Y**_{2}" for the same value of "**x**". Better yet, use

2nd-CALC >> 5:intersect >> ENTER >> ENTER >> ENTER to let the calculator find the exact coordinates of the point of intersection.

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