Problem 19 - Precalculus : Building Concepts and Connections

Question

Evaluate each expression without using a calculator. $$\ln e^{2}$$

Step-by-Step Solution

Answer

The evaluation of the expression \( \ln e^{2} \) without a calculator is 2.

Step 1: Applying the Logarithmic Identity

Start by applying the logarithmic identity \( \ln a^n = n \ln a \). On applying this identity to \( \ln e^{2} \), it results in the expression 2 \( \ln e \) .

Step 2: Evaluate \( \ln e \)

Now, remember that the natural logarithm \( \ln e \) equals to 1. This is a factual property of natural logs. So, \( \ln e \) can be replaced with 1.

Step 3: Final Calculation

Therefore, this simplifies the given expression 2 \( \ln e \) to 2 * 1, which is 2.

Key Concepts

Natural Logarithms

Natural logarithms are a special type of logarithm where the base is the mathematical constant \(e\), approximately equal to 2.71828. These logarithms are often written as \(\ln(x)\), which means the natural log of \(x\). Natural logarithms are important because they are the inverse operations of exponential functions, especially those involving \(e\). This is incredibly useful in calculus and complex mathematics, as they simplify many mathematical models and equations.

One key property of natural logarithms is that \(\ln(e) = 1\). This is because \(e\) raised to the power of 1 returns \(e\) itself, making the logarithmic operation neutral. Natural logs also adhere to all standard properties of logarithms, but they are especially convenient for continuous compounding and exponential growth rates, often showing up in calculations involving rates of change or in the analysis of complex systems, like population growth or radioactive decay.

Exponential Functions

Exponential functions have the form \(f(x) = a e^{x}\), where \(a\) is a constant and \(e\) is the base. These functions are defined for any real number \(x\) and feature a constant rate of growth. Rather than increasing linearly, exponential functions grow faster as the value of \(x\) increases.

• Exponential growth: When the exponent is positive, the function models a rapid increase.
• Exponential decay: When the exponent is negative, the function describes a similar rapid decrease.

These functions are characterized by their unique rate of growth, making them appropriate for describing a wide range of natural phenomena. They are heavily utilized in sciences to model situations such as population growth, compound interest, and radioactive decay. Understanding how to interpret and manipulate exponential expressions, especially with bases like \(e\), is crucial, as it helps unravel complex mathematical situations.

Properties of Logarithms

Logarithms have a set of powerful properties that allow for simplification and manipulation of mathematical expressions. These properties are especially handy when dealing with large numbers or complex expressions. Some of the most frequently used properties are:

• Product Property: \(\log_b(xy) = \log_b(x) + \log_b(y)\)
• Quotient Property: \(\log_b\left(\frac{x}{y}\right) = \log_b(x) - \log_b(y)\)
• Power Property: \(\log_b(x^n) = n\log_b(x)\)

These properties help break down logarithmic expressions into components that are easier to handle. In particular, the power property is what we apply when evaluating natural logarithmic forms, like \(\ln(e^2)\). Here, the base is \(e\), and by using the power property, we simplify the expression to obtain manageable parts, leading to a quick resolution of the expression's value.