Chapter 3: Problem 17
Evaluate the logarithm using the change-of-base formula. Round your result to three decimal places. $$\log _{1 / 2} 4$$
Short Answer
Expert verified
-2.000
Step by step solution
01
Setting Up the Change-of-Base Formula
Apply the change-of-base formula to re-write the equation. Given the equation \( \log _{1 / 2} 4 \), we can use the change-of-base formula so that c is 10 (this is a common base that is often used in logarithms). The change-of-base formula gives: \( \log _{1 / 2} 4 = \frac{\log 4}{\log (1/2)} \).
02
Calculating the Values
Calculate the values of \( \log 4 \) and \( \log (1/2) \). The result is: \( \frac{\log 4}{\log (1/2)} = \frac{0.6020599913}{-0.3010299957} \).
03
Division
Now compute the division. After dividing, the result is -2.
04
Rounding to Three Decimal Places
Round the result to three decimal places. Since the result is -2, and there are no decimal places in this answer, we get -2.000 as the final answer when rounded to three decimal places.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Logarithms
Logarithms are a fundamental concept in mathematics used to solve equations involving exponents. A logarithm, simply put, is an operation that helps us determine the power to which a number, called the "base," must be raised to obtain another number. For instance, in the equation \( b^x = n \), \( x \) is the logarithm of \( n \) with base \( b \). We write this as \( \log_{b}(n) = x \).
- If we say \( \log_{10}(100) = 2 \), we mean 10 raised to the power of 2 is 100.
- When we deal with different bases, it helps us solve complex problems involving growth, decay, and signal processing among other applications.
Base Conversion Using Change-of-Base Formula
The change-of-base formula is a useful tool for converting a logarithm from one base to another, making calculations easier especially when we use a calculator that typically supports only base 10 (common logarithms) or base \( e \) (natural logarithms). The formula is given by:\[\log_{b}(n) = \frac{\log_{c}(n)}{\log_{c}(b)}\]where \( c \) is the new base.
- In the original exercise, we have: \( \log _{1 / 2} 4 \) which can be transformed into \( \frac{\log 4}{\log (1/2)} \).
- By choosing base 10 (\( c = 10 \)) as a common base, we make it compatible with most calculators.
- This transformation helps simplify complex numbers and operations, translating them into a form more suited for straightforward calculation.
Applying Math Problem-Solving Skills
Problem-solving in math isn't just about plugging numbers into a formula; it involves a series of deliberate steps to analyze and solve the problem at hand effectively. Here's how you can apply problem-solving strategies to logarithmic problems:
- **Understanding the problem:** Determine what you are solving for, such as calculating a logarithm in a different base.
- **Using the right formula:** Identify the appropriate mathematical tools or formulas, like the change-of-base formula in our case.
- **Accuracy in calculation:** Be precise with your computation, ensuring you handle negative and positive values correctly. For example, when solving \( \frac{\log 4}{\log (1/2)} \), compute carefully since the logarithm of a fraction could yield negative outcomes.
- **Cross-check solutions:** Make sure your final result makes sense, such as ensuring the answer is logically rounded to three decimal places as required.