Chapter 5: Problem 92
Use the change-of-base rule to find an approximation for each logarithm. $$\log _{1 / 2} 3$$
Short Answer
Expert verified
\( \log_{1/2} 3 \approx -1.5850 \).
Step by step solution
01
Recall the Change of Base Formula
To find an approximation for a logarithm with a non-standard base, we use the change of base formula. The change of base formula for a logarithm \( \log_b a \) is given by \( \frac{\log_c a}{\log_c b} \). Typically, we use base 10 or base \( e \) (natural logarithm) for calculations.
02
Apply the Change of Base Formula
For \( \log_{1/2} 3 \), we apply the formula as follows: \( \log_{1/2} 3 = \frac{\log_{10} 3}{\log_{10} (1/2)} \). You can use base 10 or the natural logarithm (base \( e \)); here, we will use 10 for simplicity.
03
Calculate Each Logarithm
Using a calculator, find \( \log_{10} 3 \) and \( \log_{10} (1/2) \). Approximate these values to several decimal places for accuracy. \( \log_{10} 3 \approx 0.4771 \) and \( \log_{10} (1/2) \approx -0.3010 \).
04
Divide to Find the Approximation
Now divide the values obtained: \( \frac{0.4771}{-0.3010} \approx -1.5850 \). This gives us the approximate value of \( \log_{1/2} 3 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Change of Base Formula
When dealing with logarithms with non-standard bases, the change of base formula is incredibly helpful. It allows us to compute logarithms that aren't in base 10 or base \( e \). The formula states that for a given logarithm \( \log_b a \), you can express it as \( \frac{\log_c a}{\log_c b} \). This means you divide the logarithm of the desired number \( a \) by the logarithm of the base \( b \), both in the same new base \( c \).
For practical calculations, such as using a calculator, we often choose \( c = 10 \) or \( c = e \). These are the most common because calculators are typically designed to handle these bases efficiently. This process does not alter the result of the logarithm; it just makes it possible to calculate using standard tools.
For practical calculations, such as using a calculator, we often choose \( c = 10 \) or \( c = e \). These are the most common because calculators are typically designed to handle these bases efficiently. This process does not alter the result of the logarithm; it just makes it possible to calculate using standard tools.
College Algebra
College Algebra introduces students to a wide array of mathematical concepts, including functions, systems of equations, and importantly, logarithms. Logarithms are a way to represent numbers based on exponentials. They transform multiplicative processes into additive ones, which simplify the arithmetic.
- Understanding Logarithms: The concept of a logarithm revolves around finding the power to which a base must be raised to produce a given number.
- Educational Importance: Mastery of logarithms in college algebra paves the way to understanding more complex topics in mathematics and science, such as exponential growth in calculus or natural logs in chemistry.
Non-Standard Base
A non-standard base in logarithms is any base that isn't commonly used in traditional arithmetic (such as 10, or \( e \)). The base of \( \frac{1}{2} \) in \( \log_{1/2} 3 \) is an example of this, where the base isn't the usual 10 or \( e \).
Understanding base changes is crucial because:
Understanding base changes is crucial because:
- Flexibility in Problem-Solving: It helps in determining logarithmic values for a variety of bases, which is often required in real-world applications.
- Appropriate Usage: Specific fields or problems might demand calculations in non-standard bases, making this knowledge vital.