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. Logarithms - Change of Base • Example 1: Enter log512 into the calculator using base 10. Press ENTER to evaluate. Slide 2

3. Logarithms - Change of Base • Example 2: Enter log512 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. Slide 3

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

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 Slide 5

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