Chapter 5: Problem 32
\(19-44\) Use the Laws of Logarithms to expand the expression. $$ \ln \sqrt[3]{3 r^{2} s} $$
Short Answer
Expert verified
\( \frac{1}{3} \ln(3) + \frac{2}{3} \ln(r) + \frac{1}{3} \ln(s) \)
Step by step solution
01
Apply the Power Rule
The expression is given as \( \ln \sqrt[3]{3 r^{2} s} \). Recognize that the cube root can be expressed as a fractional power: \( \sqrt[3]{3 r^{2} s} = (3 r^{2} s)^{1/3} \). Use the power rule for logarithms, which states \( \ln(a^b) = b \cdot \ln(a) \), to rewrite the expression: \( \ln \left( (3r^2 s)^{1/3} \right) = \frac{1}{3} \ln(3r^2 s) \).
02
Apply the Product Rule
The expression inside the logarithm is \( \ln(3r^2 s) \). By using the product rule for logarithms, which states \( \ln(abc) = \ln(a) + \ln(b) + \ln(c) \), we can expand this to: \( \ln(3) + \ln(r^2) + \ln(s) \).
03
Apply the Power Rule Again
In \( \ln(r^2) \), apply the power rule for logarithms, \( \ln(a^b) = b \cdot \ln(a) \), which gives: \( \ln(r^2) = 2 \cdot \ln(r) \). Substitute this into the expression to get \( \ln(3) + 2 \ln(r) + \ln(s) \).
04
Combine and Simplify the Expression
Now substitute back into the expression obtained from Step 1: \( \frac{1}{3} (\ln(3) + 2 \ln(r) + \ln(s)) \). Distribute \( \frac{1}{3} \) through the expanded expression to get \( \frac{1}{3} \ln(3) + \frac{2}{3} \ln(r) + \frac{1}{3} \ln(s) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Power Rule
The Power Rule in logarithms is a powerful tool that helps simplify expressions raised to an exponent within a logarithm. Its basic form is given by: \[ \ln(a^b) = b \cdot \ln(a) \] This rule tells us that we can "pull down" the exponent in front of the logarithm as a multiplier, making complex expressions more manageable.
- First, recognize powers within logarithmic expressions.
- Apply the rule to move the exponent outside.
Product Rule
The Product Rule aids in breaking down complex logarithmic expressions involving products of multiple terms inside a logarithm. The rule states: \[ \ln(abc) = \ln(a) + \ln(b) + \ln(c) \] This tells us to split the expression into a sum of the logarithms of individual factors.
- Identify products within the logarithm.
- Split them into separate logarithmic terms.
Logarithmic Expansion
Logarithmic Expansion refers to the process of transforming a single, often complicated, logarithmic expression into a sum of simpler terms using logarithmic rules. This step-by-step expansion employs both the Power Rule and the Product Rule.
Through logarithmic expansion, we transform initial complex expressions into manageable parts that are easy to handle and solve.
- Start by recognizing complex forms like products and powers.
- Systematically apply appropriate logarithmic laws to expand the expression.
Through logarithmic expansion, we transform initial complex expressions into manageable parts that are easy to handle and solve.