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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 7, Problema 7.2.2b

2. Express the following logarithms in terms of ln 5 and ln 7.
b. ln 9.8

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1
Start by expressing 9.8 as a product or quotient of numbers involving 5 and 7. Notice that 9.8 can be written as \( 9.8 = \frac{49}{5} \) because \( 49 = 7^2 \) and \( 9.8 = 9.8 \).
Rewrite \( \ln 9.8 \) using the expression found: \( \ln 9.8 = \ln \left( \frac{49}{5} \right) \).
Use the logarithm property for division: \( \ln \left( \frac{a}{b} \right) = \ln a - \ln b \). So, \( \ln 9.8 = \ln 49 - \ln 5 \).
Express \( \ln 49 \) in terms of \( \ln 7 \) using the power rule for logarithms: \( \ln 49 = \ln (7^2) = 2 \ln 7 \).
Combine all parts to write \( \ln 9.8 \) fully in terms of \( \ln 5 \) and \( \ln 7 \): \( \ln 9.8 = 2 \ln 7 - \ln 5 \).

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Properties of Logarithms

Logarithmic properties such as the product, quotient, and power rules allow us to rewrite logarithms of complex numbers in terms of simpler components. For example, ln(ab) = ln a + ln b and ln(a^n) = n ln a. These properties are essential for expressing ln 9.8 in terms of ln 5 and ln 7.
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Change of Base Property

Prime Factorization and Approximation

Breaking down numbers into products of prime factors or close approximations helps in rewriting logarithms. Since 9.8 is not a simple product of 5 and 7, approximating or expressing 9.8 as a product or quotient involving 5 and 7 is necessary to use known logarithms effectively.
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Partial Fraction Decomposition: Repeated Linear Factors Example 4

Natural Logarithm (ln) Definition

The natural logarithm ln x is the logarithm to the base e, where e is Euler's number (~2.718). Understanding ln as the inverse of the exponential function helps in manipulating and combining logarithmic expressions, especially when expressing one logarithm in terms of others.
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Derivative of the Natural Logarithmic Function