3.4 - Derivatives of Exponential and Logarithmic Functions
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Derivatives of Exponential Functions
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Today, we will start with the derivatives of exponential functions. Let's begin with the natural exponential function, which is \( e^x \). Does anyone know what the derivative of \( e^x \) is?
I think it's just \( e^x \), right?
Exactly! The derivative of \( e^x \) is indeed \( e^x \). This means that the rate at which \( e^x \) changes is proportional to its current value, which is a unique property of the exponential function.
What about other bases? Is there a formula for that?
Great question! For an exponential function with a different base, say \( a^x \), the derivative is given by \( \frac{d}{dx}[a^x] = a^x \ln(a) \). So, if you know the base, you can easily compute the derivative!
Can you give an example with a specific base?
Sure! Let’s take \( f(x) = 2^x \). The derivative would be \( \frac{d}{dx}[2^x] = 2^x \ln(2) \).
So, if we substitute a value like \( x = 1 \), would it help us find the rate of change?
Exactly! If you plug in \( x = 1 \), you'd get \( 2^1 \ln(2) \), which gives you the instantaneous rate of change at that point.
Derivatives of Logarithmic Functions
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now, let’s transition to logarithmic functions. Who can tell me the derivative of \( \ln(x) \)?
I believe it's \( \frac{1}{x} \).
Correct! The derivative of \( \ln(x) \) is \( \frac{1}{x} \). This explains how the natural logarithm grows slower than polynomial functions.
What about logarithms with different bases?
For logarithms to any base, such as \( \log_a(x) \), the derivative is given by \( \frac{1}{x \, \ln(a)} \). This means that the growth rate depends on both the input value and the logarithmic base.
Could you show a practical application for finding the derivative of a logarithm?
Certainly! In real-life situations, such as calculating pH in chemistry, we often use logarithmic functions where understanding the rate of change is crucial. For instance, if we're dealing with \( \log_{10}(x) \), we'd apply the formula \( \frac{1}{x \, ext{ln}(10)} \).
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
In this section, we explore how to differentiate exponential functions such as e^x and a^x, along with logarithmic functions including ln(x) and log_a(x). Understanding these derivatives is foundational for advanced calculus concepts and real-world applications.
Detailed
Detailed Summary
This section delves into the derivatives of exponential and logarithmic functions, key components of calculus that are crucial for various applications in mathematics, physics, engineering, and economics. Understanding how to differentiate these functions allows for deeper insights into how they change over time.
Key Points Covered:
- Exponential Functions:
- The derivative of the exponential function, specifically the natural exponential function, is given by:
- If \( f(x) = e^x \), then \( \frac{d}{dx}[e^x] = e^x \).
-
For other bases, \( f(x) = a^x \) (where \( a \) is a constant), the derivative is:
- \( \frac{d}{dx}[a^x] = a^x \ln(a) \).
- Logarithmic Functions:
- The derivative for the natural logarithmic function is crucial:
- If \( f(x) = \ln(x) \), then \( \frac{d}{dx}[\ln(x)] = \frac{1}{x} \).
- For the logarithm to any base \( a \), the derivative is expressed as:
- If \( f(x) = \log_a(x) \), then \( \frac{d}{dx}[\log_a(x)] = \frac{1}{x\ln(a)} \).
These derivatives form the foundation for many applications in higher-level calculus and real-world scenarios where exponential growth and decay or logarithmic measures are relevant.
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Derivatives of Exponential Functions
Chapter 1 of 2
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
- Exponential Functions:
If 𝑓(𝑥) = 𝑒𝑥, then
𝑑 [𝑒𝑥] = 𝑒𝑥
𝑑𝑥
More generally, if 𝑓(𝑥) = 𝑎𝑥 (where 𝑎 is a constant), then
𝑑 [𝑎𝑥] = 𝑎𝑥ln(𝑎)
𝑑𝑥
Detailed Explanation
This chunk introduces derivatives of exponential functions. The first formula states that if the function f(x) equals e raised to the power of x, then the derivative of this function is simply e raised to the power of x. This is a unique property of the mathematical constant 'e'. For any exponential function where a is a constant (like 2, 10, etc.), the derivative is given by multiplying the function itself, ax, by the natural logarithm of a (ln(a)). Essentially, we are finding how quickly this function grows with respect to x.
Examples & Analogies
Think of investing money in a bank that offers compound interest, which grows exponentially. If you invest an amount, say $1000, it might grow as 1000e^x, where x represents time. The derivative tells you how fast your investment is growing at any moment. If you are looking at your account balance daily, the 'rate of change' of your balance represents the bank's growth contribution, and understanding this helps you make informed financial decisions.
Derivatives of Logarithmic Functions
Chapter 2 of 2
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
- Logarithmic Functions:
If 𝑓(𝑥) = ln(𝑥), then
𝑑 1
[ln(𝑥)] =
𝑑𝑥 𝑥
If 𝑓(𝑥) = log_a(𝑥), then
𝑑 1
[log_a(𝑥)] =
𝑑𝑥 𝑥ln(𝑎)
Detailed Explanation
This chunk discusses the derivatives of logarithmic functions. If the function f(x) is the natural logarithm of x (ln(x)), its derivative is the reciprocal of x. This means as x increases, the rate of change of ln(x) decreases. For logarithms with a different base (a), the derivative is also the reciprocal of x, but multiplied by the natural logarithm of the base (ln(a)). This property is useful when transforming or rewriting functions in calculus.
Examples & Analogies
Consider the process of measuring sound intensity. You often use a decibel scale, which is logarithmic; small changes in the sound’s power level are compared to a baseline intensity. When teaching someone about how sound levels change, you can explain that while our perception adjusts logarithmically, the derivative gives us the exact rate at which our understanding of sound power changes at a given level. This helps us to quantify differences in sound terms that are more intuitive to ear and less linked to raw power which might be harder to grasp.
Key Concepts
-
Exponential Derivative: The derivative of \( e^x \) is \( e^x \).
-
General Exponential Derivative: For \( a^x \), the derivative is \( a^x \ln(a) \).
-
Natural Logarithm Derivative: The derivative of \( \ln(x) \) is \( \frac{1}{x} \).
-
Logarithmic Derivative: For \( log_a(x) \), the derivative is \( \frac{1}{x \, ext{ln}(a)} \).
Examples & Applications
Example 1: Differentiate \( f(x) = 3^x \). The derivative is \( f'(x) = 3^x \ln(3) \).
Example 2: Differentiate \( g(x) = \ln(5x) \). The derivative is \( g'(x) = \frac{5}{5x} = \frac{1}{x}. \)
Example 3: Find the derivative of \( h(x) = 2^x + 3^x \). The derivative is \( h'(x) = 2^x \ln(2) + 3^x \ln(3) \).
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
For e to the x, just take a hack, the same you get right back on track!
Acronyms
E.L.L. - Exponential, Logarithmic, Linear derivatives.
Memory Tools
For a derivative of a base a, remember the form: a^x ln(a)! This works any day.
Stories
Imagine a plant growing exponentially; as time goes by, its growth rate matches its height, that's e^x. For a logarithm, it's like counting levels on a ladder, every step is slower, reflecting 1/x as you climb higher.
Flash Cards
Glossary
- Exponential Function
A mathematical function of the form f(x) = a^x, where a is a positive constant.
- Natural Exponential Function
The exponential function with base e, denoted as f(x) = e^x.
- Derivative
A measure of how a function changes as its input changes.
- Logarithmic Function
A function of the form f(x) = log_a(x), which is the inverse of the exponential function.
- Natural Logarithm
The logarithm with base e, denoted as ln(x).
Reference links
Supplementary resources to enhance your learning experience.