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Sullivan Algebra and Trigonometry: Section 6.4 Logarithmic Functions. Objectives of this Section Change Exponential Expressions to Logarithmic Expressions and Visa Versa Evaluate the Domain of a Logarithmic Function Graph Logarithmic Functions Solve Logarithmic Equations.
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Sullivan Algebra and Trigonometry: Section 6.4Logarithmic Functions • Objectives of this Section • Change Exponential Expressions to Logarithmic Expressions and Visa Versa • Evaluate the Domain of a Logarithmic Function • Graph Logarithmic Functions • Solve Logarithmic Equations
The Logarithmic Function is the inverse of the exponential function. Therefore: Domain of logarithmic function = Range of exponential function = (0, ) Range of logarithmic function = Domain of exponential function = (- , )
The graph of a log function can be obtained using the graph of the corresponding exponential function. The graphs of inverse functions are symmetric about y = x. (0, 1) (1, 0) a > 1
(0, 1) (1, 0) 0 < a < 1
1. The x-intercept of the graph is 1. There is no y-intercept. 2. The y-axis is a vertical asymptote of the graph. 3. A logarithmic function is decreasing if 0 < a < 1 and increasing if a > 1. 4. The graph is smooth and continuous, with no corners or gaps.
The logarithmic function with base e is called the natural logarithm. This function occurs so frequently it is given its own symbol: ln
(e, 1) (1, 0)
x = 3 (e + 3, 1) (4, 0) Domain: x > 3 (since x - 3 > 0) Range: All Real Numbers Vertical Asymptote: x = 3
To solve logarithmic equations, first rewrite the equation in exponential form. Example: Solve