If your data seems to fit a wave, then your best fit equation is likely achieved with trigonometic regression. The most accurate way to make predictions about a data’s future behavior is to find an equation that best fits the data. While a scatter plot can give you an idea of the function’s behavior, it isn’t very good for predictions, unless you throw in a bit of guesswork. You could probably also guess that your data is trigonometric by looking at the up and down pattern of the y-values (for example, 18 to 17 and back to 18 again).

If you view a scatter plot on the TI-89, you’ll discover that the dots travel in waves. Trigonometric regression is performed when a scatter plot of data suggests a trigonometric function, or wave like appearance. That’s How to find Linear Regression on TI-89! 2. Step 10: Insert the calculator’s result into the equation y’ = ax+b: y’ = -2.9x+15.06 The calculator returns the value of a and b for you to enter into the equation y’=ax+b (in our equation, a = -2.9 and b = 15.06). Enter ALPHA ) 2: this puts c2 into the space. Step 9: Press the down arrow key to the next row (y). This tells the calculator where your x-variables are.

Enter c1 using the alphanumeric keypad (the ALPHA button then a close parenthesis ), then 1). Step 8: Press the down arrow key to the next row (x).

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