Problem 26 - Precalculus : Building Concepts and Connections

Question

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

Step-by-Step Solution

Answer

The evaluated expression is \(w\). This is a simple and straightforward result, coming from the properties of natural logarithm and \(e\).

Step 1: Recall Properties of Logarithms

Recall the primary properties of logarithms which indicate that the logarithm of a number to a certain base is just the exponent. In this case, the base of the log function is \(e\), the base of the natural logarithm.

Step 2: Apply the Property

According to the logarithm property, \(ln(e^{w}) = w\).

Key Concepts

Logarithm Rules

Understanding the rules governing logarithms is essential for solving many mathematical problems involving exponents and logarithmic functions. Logarithm rules, also known as log laws, make it easier to manipulate and simplify logarithmic expressions.

Some fundamental logarithm rules include:

• The Product Rule: For any positive numbers a, b, and base c, the logarithm of the product is the sum of the logarithms: \( \log_c(a \times b) = \log_c(a) + \log_c(b) \).
• The Quotient Rule: For any positive numbers a, b under the same base c, the logarithm of the quotient is the difference of the logarithms: \( \log_c\left(\frac{a}{b}\right) = \log_c(a) - \log_c(b) \).
• The Power Rule: When raising a logarithm to a power, the exponent can be brought to the front: \( \log_c(a^b) = b \cdot \log_c(a) \).

Using these rules helps simplify complex logarithmic equations and expressions. For example, the exercise \(\ln e^{w}\) demonstrates the application of the Power Rule, allowing the exponent w to come to the front, which in the case of a natural logarithm directly simplifies to w itself.

Natural Logarithms

A natural logarithm, denoted as \(\ln\)), is a logarithm with the base e, where e is an irrational and transcendental number approximately equal to 2.71828. It's incredibly significant in various fields of science and mathematics because it describes growth processes, like population growth, interest calculations, or the spread of diseases.

The natural logarithm has several intriguing properties. For instance, \(\ln(e) = 1\) because the base of the natural logarithm is e. Similarly, \(\ln(1) = 0\), which follows from the definition of logarithms: the power to which the base must be raised to yield 1 is 0, since \(e^0 = 1\).

Another salient natural logarithm property used in our exercise is \(\ln(e^x) = x\). This characteristic arises from the inverse relationship between the \(e^x\) function and the natural logarithm. Essentially, when the base e of the exponential function is the same as the base for the logarithm, the two operations cancel each other out, leaving the exponent as the result.

Exponential Functions

Exponential functions form the backbone of many natural and man-made phenomena, from compound interest in finance to radioactive decay in physics. An exponential function is written as \(f(x) = a^x\), where a is a constant base and x is the exponent.

The base e is particularly special and widely used, leading to exponential functions of the form \(e^x\), commonly known as the natural exponential function. It's the inverse of the natural logarithm and has a unique property: its rate of growth is proportional to its current value, which makes its derivative particularly elegant—equal to \(e^x\) itself.

Because of their inverse relationship, exponential functions and logarithms are often used to solve equations involving growth and decay. In the context of our original exercise, the function \(e^w\) is an exponential function with base e. When this function appears inside a natural logarithm, as in \(\ln(e^w)\), the logarithm’s action reverses the exponentiation, reducing the expression to simply w, as per the rules of logarithms.