Chapter 5: Problem 75
Find the logarithm using natural logarithms and the change-of-base formula. $$\log _{3} 12$$
Short Answer
Expert verified
Using change-of-base formula, \(\log_3 12 \approx 2.262\).
Step by step solution
01
Understand the change-of-base formula
The change-of-base formula for logarithms states that \(\log_a b = \frac{\log_c b}{\log_c a}\), where \(a\) and \(b\) are positive numbers and \(c\) is the new base, typically natural logarithms (base \(e\)).
02
Apply the change-of-base formula
To find \(\log_3 12\), use the change-of-base formula with natural logarithms (base \(e\)). This transforms \(\log_3 12\) to \(\frac{\ln 12}{\ln 3}\).
03
Calculate the natural logarithms
Find the natural logarithms of 12 and 3. Using a calculator: \(\ln 12 \approx 2.4849\) and \(\ln 3 \approx 1.0986\).
04
Divide the natural logarithms
Divide the results from Step 3: \(\frac{2.4849}{1.0986} \approx 2.262\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
logarithms
A logarithm answers the question: 'To what power must we raise a specific base to obtain a given number?' For example, \(\text{log}_2 8 \) asks, 'To what power must 2 be raised to get 8?' The answer is 3, because \(2^3 = 8\). This concept is essential in various fields such as science, engineering, and finance. Common logarithms use base 10 and are denoted as \(\text{log}\), while natural logarithms use base \(e\) and are denoted as \(\text{ln}\).Logarithms have several properties that make them useful for simplifying complex calculations:
- Product Rule: \(\text{log}_b (XY) = \text{log}_b X + \text{log}_b Y\).
- Quotient Rule: \(\text{log}_b (X/Y) = \text{log}_b X - \text{log}_b Y\).
- Power Rule: \(\text{log}_b (X^Y) = Y \text{log}_b X\).
natural logarithms
Natural logarithms are a specific type of logarithm that uses the mathematical constant \(e\) (approximately 2.718) as the base. They are often written as \( \text{ln} \) instead of \( \text{log}_e \). Natural logarithms are particularly useful in calculus and mathematical modeling because the derivative and integral of \( \text{ln} x \) have simple and elegant forms.Here's why they are important:
- **Growth and Decay**: Many natural processes, like population growth and radioactive decay, are modeled using the natural logarithm because they involve continuous growth or decay.
- **Compound Interest**: Financial calculations involving continuously compounded interest also utilize natural logarithms.
base conversion
Base conversion in logarithms allows us to change the base of a logarithmic expression to another base that is more convenient for computation. The change-of-base formula states:\[ \text{log}_a b = \frac{\text{log}_c b}{\text{log}_c a} \]Where \ a \ and \ b \ are positive numbers and \ c \ is the new base. This method is particularly helpful when calculators are involved, as they typically only provide logarithms to base 10 (common logarithm) and base \( e \) (natural logarithm).To apply this in the given exercise, we converted \( \text{log}_3 12 \) to a fraction of natural logarithms:\[ \text{log}_3 12 = \frac{\text{ln} 12}{\text{ln} 3} \]This converts our original base 3 logarithm into base \( e \), which can be easily computed using a calculator.With the values \( \text{ln} 12 \) approximately 2.4849 and \( \text{ln} 3 \) approximately 1.0986, the division yields approximately 2.262. This method is efficient and reliable for solving logarithms with unconventional bases.