Problem 38 - College Algebra and Calculus: An Applied Approach

Question

Evaluate the expression without using a calculator.\(\ln e^{10}\)

Step-by-Step Solution

Answer

The value of \(\ln e^{10}\) is 10.

Step 1: Apply Logarithmic Identity

Using the logarithmic identity \(\ln a^b = b \ln a\), the expression \(\ln e^{10}\) can be rewritten as \(10 \ln e\).

Step 2: Evaluate \(\ln e\)

The value of \(\ln e\) is 1. This is a widely known fact as the natural logarithm base is \(e\). So, the expression becomes \(10 \times 1\).

Step 3: Simplify the Result

Multiplying 10 by 1 results in 10. So the value of \(\ln e^{10}\) is 10.

Key Concepts

Natural Logarithm

The natural logarithm is a specific type of logarithm that has the base of the constant e, approximately equal to 2.71828. Unlike the more commonly known base-10 logarithm, the natural logarithm is denoted as \( \ln \). It is a vital concept in higher mathematics because it has unique properties that simplify complex calculations.
Natural logarithms are used extensively in calculus, scientific calculations, and in various mathematical models such as exponential growth and decay.
One of the key characteristics of the natural logarithm is its relationship with the number \( e \). In simple terms, \( \ln e \) equals 1 because the base raised to the power of 1 results in e itself. Understanding the behavior of natural logarithms opens doors to easier manipulation and evaluation of expressions like \( \ln e^{10} \).

Logarithmic Identity

Logarithmic identities are essential tools that enable the simplification of complex mathematical expressions. One such identity is \( \ln a^b = b \ln a \). This specific identity helps us transform expressions where the argument of the logarithm is an exponential value.
Here's a breakdown of how it works:

• Take the logarithm of an exponent, \( a^b \) becomes \( b \ln a \).
• The power b acts as a multiplier for the logarithm of the base a.

This property stems from expansion rules involving the exponent inside the log. It allows easier computation by transforming an exponential form into a linear multiplication problem, as we see in \( \ln e^{10} \), which simplifies to \( 10 \times \ln e \).

Evaluate Expression

Evaluating expressions without calculators benefits significantly from strong algebraic manipulations and identities. When you need to evaluate \( \ln e^{10} \), you can effectively use logarithmic properties to simplify the process.
Start with the identity we discussed: \( \ln e^{10} \) translates to \( 10 \ln e \). Since we know \( \ln e = 1 \), it becomes quick multiplication: 10 multiplied by 1, which equals 10.
This simplification is not just a trick but a practical application of mathematical properties. Recognizing the parameters of natural logs and employing identities turns the seemingly cumbersome into straightforward arithmetic.