Derivative Of 3 Ln X

Unveiling the Derivative of 3ln(x): A Comprehensive Guide

Understanding derivatives is crucial for anyone studying calculus. This article delves into finding the derivative of the function 3ln(x), explaining the process step-by-step and exploring the underlying mathematical principles. We will cover the basics of differentiation, the properties of logarithms, and finally, arrive at a clear and concise solution, along with explanations of related concepts. This guide is designed to be accessible to students with varying levels of calculus experience, ensuring a comprehensive understanding of this important concept.

Introduction to Derivatives and Logarithmic Functions

Before diving into the specific problem, let's establish a foundational understanding of derivatives and logarithmic functions. The derivative of a function measures its instantaneous rate of change at any given point. Geometrically, it represents the slope of the tangent line to the function's graph at that point. We denote the derivative of a function f(x) as f'(x) or df/dx.

Logarithmic functions, specifically the natural logarithm (ln), are inverse functions of exponential functions. The natural logarithm, written as ln(x) or logₑ(x), is the logarithm to the base e, where e is the mathematical constant approximately equal to 2.71828. A key property of logarithms that we will utilize is the power rule: ln(aˣ) = x ln(a). This rule is crucial in simplifying logarithmic expressions and applying differentiation rules effectively.

Understanding the Power Rule and Chain Rule of Differentiation

Two fundamental rules of differentiation are essential for solving our problem: the power rule and the chain rule.

• The Power Rule: The derivative of xⁿ is nxⁿ⁻¹, where n is any real number. This rule is straightforward for polynomial terms.

• The Chain Rule: The chain rule is used to differentiate composite functions. If we have a function y = f(g(x)), then its derivative is dy/dx = f'(g(x)) * g'(x). In simpler terms, we differentiate the outer function, leaving the inner function intact, and then multiply by the derivative of the inner function.

Deriving the Derivative of 3ln(x) Step-by-Step

Now, let's tackle the main problem: finding the derivative of 3ln(x). We'll use the properties of logarithms and the rules of differentiation we've discussed.

Step 1: Applying the Constant Multiple Rule

The constant multiple rule states that the derivative of a constant multiplied by a function is equal to the constant multiplied by the derivative of the function. In our case:

d/dx [3ln(x)] = 3 * d/dx [ln(x)]

This simplifies our problem to finding the derivative of ln(x).

Step 2: Differentiating the Natural Logarithm

The derivative of the natural logarithm function ln(x) is 1/x. This is a fundamental result in calculus, often derived using the definition of the derivative and properties of exponential and logarithmic functions. A rigorous proof involves the limit definition of the derivative and the properties of the exponential function. For this article, we will accept this as a given.

Step 3: Combining the Results

From Step 1 and Step 2, we can now write the final derivative:

d/dx [3ln(x)] = 3 * (1/x) = 3/x

Therefore, the derivative of 3ln(x) is 3/x.

A Deeper Dive into the Derivative of ln(x)

Let's delve a little deeper into the derivation of the derivative of ln(x), although we've accepted it as given above for simplification. The derivative can be found using the limit definition of the derivative:

f'(x) = lim (h→0) [(f(x + h) - f(x))/h]

Applying this to f(x) = ln(x):

f'(x) = lim (h→0) [(ln(x + h) - ln(x))/h]

Using logarithmic properties (ln(a) - ln(b) = ln(a/b)):

f'(x) = lim (h→0) [ln((x + h)/x)/h]

f'(x) = lim (h→0) [ln(1 + h/x)/h]

Now, we can use the limit property: lim (u→0) [ln(1 + u)/u] = 1

Let u = h/x. As h approaches 0, u also approaches 0. So, we can rewrite:

f'(x) = lim (u→0) [ln(1 + u)/(ux)] = (1/x) * lim (u→0) [ln(1 + u)/u] = (1/x) * 1 = 1/x

This confirms that the derivative of ln(x) is indeed 1/x.

Applications of the Derivative of 3ln(x)

The derivative, 3/x, has various applications in different fields. For instance:

• Economics: It can be used in marginal cost analysis where the cost function involves logarithmic terms.

• Physics: Derivatives are frequently used to describe rates of change in physical systems, and logarithmic functions often model natural processes.

• Engineering: Optimization problems often involve finding the maximum or minimum of functions, requiring the use of derivatives.

• Computer Science: Derivatives are crucial in algorithms like gradient descent used in machine learning.

Frequently Asked Questions (FAQs)

Q1: What is the domain of the function 3ln(x)?

A1: The natural logarithm is only defined for positive values of x. Therefore, the domain of 3ln(x) is (0, ∞).

Q2: What is the derivative of ln(x²) ?

A2: Using the chain rule and the property ln(x²) = 2ln(x), we get d/dx[ln(x²)] = d/dx[2ln(x)] = 2/x. Alternatively, using the chain rule directly, we get (1/x²) * 2x = 2/x.

Q3: Can we find the derivative of 3ln(|x|) ?

A3: Yes. The derivative of ln(|x|) is 1/x. Therefore, the derivative of 3ln(|x|) is 3/x. Note that the absolute value ensures the function is defined for both positive and negative x (except x=0).

Q4: What is the significance of the derivative in relation to the original function?

A4: The derivative represents the slope of the tangent line at any point on the graph of the original function. It indicates the instantaneous rate of change of the function at that specific point. It’s a crucial concept for optimization, analysis of rates of change, and understanding the behavior of functions.

Conclusion

Finding the derivative of 3ln(x) involves applying fundamental rules of differentiation. The process highlights the importance of understanding the chain rule, constant multiple rule, and the derivative of the natural logarithm. The result, 3/x, has wide-ranging applications in various fields where logarithmic functions and rates of change are crucial aspects of the analysis. This in-depth explanation provides a solid foundation for further exploration of calculus and its applications. Remember that consistent practice and a firm grasp of the basic rules are essential to mastering the concepts of differentiation.