1. Logarithms - Change of Base When working with logarithms, we sometimes want to enter the log into the calculator. If the base is 10 or e, this is done with a simple key stroke, LOG for log base 10, and LN for log base e (natural log). To enter a log to a base other than 10 or e, use the change of base formula: Select base “a” to be either 10 or e.

2. Slide 2 Logarithms - Change of Base Example 1: Enter log 5 12 into the calculator using base 10. Press ENTER to evaluate.

3. Slide 3 Logarithms - Change of Base Example 2: Enter log 5 12 into the calculator using base e. Press ENTER to evaluate. Note that the new base is arbitrary. The same answer resulted using base 10 and base e.

4. Slide 4 Example 3: Logarithms - Change of Base Sketch the graph of Type the function into Y1 Select the ZOOM|ZStandard window.

5. Slide 5 Logarithms - Change of Base For a better window, press WINDOW and make the following changes: Press GRAPH to obtain... Note that there is a vertical asymptote at x = 2

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