Overview
This lecture demonstrates how to use the "STO→" (store) button on the TI-84 calculator to evaluate function values numerically, particularly for estimating limits.
Using the STO→ Button on TI-84
- The STO→ button stores a numerical value into a variable (e.g., x) on the calculator.
- To store a value, input the number, press STO→, then the variable key (x), and hit enter.
- The calculator now uses the stored value whenever the variable is referenced.
- You can verify the stored value by pressing the variable key and hitting enter.
Evaluating a Limit Numerically
- The example estimates the limit as x approaches 7 of the function 1/(x–7) using the calculator.
- For the right-hand limit, choose x values just greater than 7 (e.g., 7.1, 7.01, 7.001, 7.0001).
- Store each x value using STO→ and then evaluate the function 1/(x–7).
- Use parentheses around the denominator when entering the function.
- Previous function entries can be quickly recalled using the "second" and "enter" buttons.
- The outputs for the given x values demonstrate that as x approaches 7 from the right, the function values increase rapidly (10, 100, 1000, 10000).
Interpreting the Results
- The increasing outputs show that the function 1/(x–7) approaches positive infinity as x approaches 7 from the right.
- The process demonstrates numerical estimation of a limit using the calculator.
Key Terms & Definitions
- STO→ (Store Button) — Calculator function used to assign a specific value to a variable.
- Limit — The value that a function approaches as the input (x) approaches some value.
- Right-hand Limit — The value a function approaches as x approaches from values greater than the target value.
Action Items / Next Steps
- Practice using the STO→ button to store values and evaluate functions for different x values.
- Try estimating left-hand limits and other types of limits with the calculator.