Problem 15 - College Algebra and Calculus: An Applied Approach

Question

Write the logarithm in terms of natural logarithms.\(\log _{10} 5\)

Step-by-Step Solution

Answer

Therefore, \( \log _{10} 5 = \frac{\ln 5}{\ln 10} \).

Step 1: Identify the Current Base and Number

In the logarithm \( \log _{10} 5 \), the base is 10 and the number is 5.

Step 2: Apply the Change of Base Formula.

We replace the base 10 logarithm with a natural logarithm using the change of base formula. This turns \( \log _{10} 5 \) into \( \frac{\ln 5}{\ln 10} \).

Key Concepts

Understanding Logarithms

Logarithms are one of the fundamental concepts in algebra that students encounter. In simple terms, a logarithm answers the question: 'To what power do we raise a base number to obtain a certain value?' The expression \( \log_b{a} \) tells us the power, or exponent, which the base \( b \) is raised to in order to get the number \( a \)..

For example, when we say \( \log_{10}{100} = 2 \) we're saying that 10 raised to the power of 2 gives us 100. Logarithms have various properties that make working with exponential expressions easier. These include the product, quotient, and power rules, which allow us to multiply, divide, and raise powers inside a logarithmic expression, respectively.

Understanding how to manipulate and interpret logarithms is crucial for solving a multitude of problems in mathematics, especially when dealing with exponential growth and decay, interest calculations, and in scientific fields where quantities can vary over large ranges.

The Elegance of Natural Logarithms

Natural logarithms are a special category of logarithms where the base is the mathematical constant \( e \) (approximately 2.71828). We denote natural logarithms with the symbol \( \ln \). So, for any positive number \( a \) the natural logarithm \( \ln(a) \) answers: 'To what power must \( e \) be raised to yield the number \( a \)?'..

Why are natural logarithms so important? Well, the number \( e \) surfaces naturally in various areas of mathematics, including calculus, complex analysis, and financial mathematics. For instance, when you deal with continuous growth or decay like population growth or radioactive decay, natural logarithms are inherently part of the equations that model these phenomena. The change of base formula used in the exercise, \( \frac{\ln 5}{\ln 10} \) is a practical application of natural logarithms, enabling you to convert from one base to another effortlessly.

Mastering Algebraic Operations with Logarithms

Algebraic operations such as addition, subtraction, multiplication, and division are the building blocks of algebra. With logarithms, these operations have unique properties that allow us to manipulate expressions and equations in clever ways. For example, the logarithm of a product is equal to the sum of the logarithms of its factors. This is known as the product rule: \( \log_b(m \cdot n) = \log_b(m) + \log_b(n) \)..

Similarly, the logarithm of a quotient is the difference of the logarithms, which is the quotient rule: \( \log_b(\frac{m}{n}) = \log_b(m) - \log_b(n) \) . And the power to which a number is raised can be 'pulled out' in front of the logarithm, the power rule: \( \log_b(m^n) = n \cdot \log_b(m) \) .

These properties streamline solving complex problems by transforming them into more manageable pieces. Whether you are multiplying large numbers or solving for an unknown exponent, understanding these algebraic operations within the context of logarithms is a potent tool in your mathematical arsenal.