Chapter 5: Problem 4
Evaluate the expression. $$ \log \frac{1}{\sqrt{1000}} $$
Short Answer
Expert verified
The value of the expression is \(-\frac{3}{2}\).
Step by step solution
01
Rewrite the Expression
To simplify the expression, let's rewrite the given logarithmic expression: \( \log \frac{1}{\sqrt{1000}} \). This can be rewritten as \( \log (1000^{-1/2}) \) because \( \sqrt{1000} = 1000^{1/2} \) and the reciprocal is the negative exponent: \( \frac{1}{x} = x^{-1} \).
02
Apply the Power Rule of Logarithms
Using the power rule of logarithms, which states that \( \log(a^b) = b \log(a) \), we can rewrite the expression as \(-\frac{1}{2} \cdot \log(1000) \).
03
Evaluate Logarithm of 1000
Recognize that 1000 is \( 10^3 \). By using the property of logarithms, \( \log(a^b) = b \log(a) \), we compute \( \log(1000) = \log(10^3) = 3 \log(10) \). Since \( \log(10) = 1 \) (for common logarithm with base 10), we find that \( \log(1000) = 3 \cdot 1 = 3 \).
04
Calculate the Result
Substitute back the value of \( \log(1000) = 3 \) into our expression from Step 2: \(-\frac{1}{2} \cdot 3 = -\frac{3}{2} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Power Rule of Logarithms
The power rule of logarithms is a fundamental tool that simplifies logarithmic expressions involving exponents. The rule states that if you have a logarithm of a number raised to an exponent, such as \( \log(a^b) \), you can bring the exponent down as a coefficient in front of the logarithm. Mathematically, it's expressed as:
For example, in our exercise, we simplified \( \log(1000^{-1/2}) \) to \( -\frac{1}{2} \cdot \log(1000) \). This conversion helps because we can focus on evaluating the simpler logarithm, \( \log(1000) \), separately.
- \( \log(a^b) = b \cdot \log(a) \)
For example, in our exercise, we simplified \( \log(1000^{-1/2}) \) to \( -\frac{1}{2} \cdot \log(1000) \). This conversion helps because we can focus on evaluating the simpler logarithm, \( \log(1000) \), separately.
Properties of Logarithms
Logarithms have several properties that make them a powerful tool in mathematics, enabling the simplification and solving of complex equations.
Here are some key properties:
Understanding these properties allows handling different forms of expressions simply by applying the right rule.
Here are some key properties:
- Product Rule: \( \log(ab) = \log(a) + \log(b) \)
- Quotient Rule: \( \log\left(\frac{a}{b}\right) = \log(a) - \log(b) \)
- Power Rule: \( \log(a^b) = b \cdot \log(a) \)
- Change of Base Formula: \( \log_b(a) = \frac{\log_c(a)}{\log_c(b)} \)
Understanding these properties allows handling different forms of expressions simply by applying the right rule.
Common Logarithm
A common logarithm is a logarithm with the base of 10 and is often denoted simply as \( \log(x) \) rather than \( \log_{10}(x) \). It's commonly used in many scientific and engineering disciplines due to the simplicity when dealing with powers of 10.
For example, the common logarithm of 10 is 1 because 10 raised to the power of 1 equals 10: \( \log(10) = 1 \). This property made it straightforward in our exercise to compute \( \log(1000) \) because 1000 is \( 10^3 \), leading to:
For example, the common logarithm of 10 is 1 because 10 raised to the power of 1 equals 10: \( \log(10) = 1 \). This property made it straightforward in our exercise to compute \( \log(1000) \) because 1000 is \( 10^3 \), leading to:
- \( \log(10^3) = 3 \cdot \log(10) = 3 \cdot 1 = 3 \)