7.2.2 The Natural Base, e
Key Objectives • Use the number e to write and graph exponential functions representing real-world situations. • Solve equations and problems involving e or natural logarithms. Key Terms • A natural logarithm is a logarithm with base e , written as ln. • The natural logarithmic function is the function f ( x ) = ln x , which is the inverse of the natural exponential function f ( x ) = e x .
The constant e is an irrational number. Its approximate value is 2.71828 and it is the base of the natural log, denoted ln.
Example 1 Graphing Exponential Functions Use a calculator to evaluate a natural exponential function and round the values to the nearest tenth.
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