# Natural Logarithmic Function

## The Power of the Natural Logarithmic Function: How to Solve Equations and Understand Its Impact

If you've ever wondered about the return on your investment, knowing the natural logarithmic function can be essential. Let's dive into the curious relationship between the natural logarithmic and exponential functions, and how to graph and convert these functions for real-world applications.

Defining the Natural Logarithmic Function

Remember that e, also known as Euler's number, is the base of the exponential growth and decay function. The natural logarithmic function, ln(x), is simply the inverse of this function. This can be read as "f of x is the natural log of x". Essentially, it tells us the amount of time needed to reach a certain amount of growth.

Graphing the Natural Logarithmic Function

Visually, the natural log is the reflection of the exponential growth function over a line. If we graph both functions, they will appear as mirror images of each other. While the exponential function shows us how much something has grown over time, the natural log reveals the time needed for that growth to occur.

Let's explore an example to better understand the power of continuous compounding. Imagine investing \$1000 in chocolate with a staggering interest rate of 100%. If we want to see our initial investment grow 20 times, it would only take approximately 3 years. That's the power of continuous compounding!

The Domain of the Natural Logarithmic Function

Similar to the regular logarithmic function, the natural log has no y-intercept and its x-intercept is at x=1. However, the domain of this function is all positive real numbers, while the range is all real numbers.

Why is e the Base of the Natural Logarithmic Function?

There are two main reasons why e is chosen as the base of the natural log function. Firstly, the natural log and exponential functions are inverses of each other, making their bases equal. Secondly, the natural log represents the natural amount of time it takes for growth to occur. Therefore, asking for the natural log of e is equivalent to asking for the time it takes for the function to reach its natural growth of e.

Converting Logarithmic Functions

We can convert logarithmic functions to different bases using the Proportion Rule, which states that log_b(x) = log_a(x)/log_a(b). This can be helpful when comparing different functions. For instance, to convert log_2(x) to ln(x), we would use log_2(x) = log_e(x)/log_e(2). Simplifying further, we get ln(x)/ln(2), indicating that log_2(x) is equal to ln(x) divided by ln(2).

Derivatives and Integrals of the Natural Logarithmic Function

The derivative of the natural logarithmic function is 1/x, and its integral is xln(x)-x. These properties are useful in solving advanced mathematical problems and real-world applications.

Key Takeaways

• The natural logarithmic and exponential functions are inverses of each other
• The natural log of x represents the time it takes for growth to occur
• The natural log function has no y-intercept and x-intercept at x=1, with a domain of all positive real numbers
• The base of e is used for the natural log function due to its relation with the exponential function and representation of natural time
• Logarithmic functions can be converted using the Proportion Rule
• The derivative and integral of the natural log function are 1/x and xln(x)-x, respectively

In conclusion, the natural logarithmic function plays a significant role in various fields, such as finance, science, and engineering. Understanding its definition, graphing, conversion, and properties can help us solve complex problems and gain a deeper appreciation for the natural world.

## How to Solve Natural Logarithmic Equations

Solving natural logarithmic equations may seem daunting, but by following a few simple steps, the process can be easily understood and executed.

### Step 1: Isolate the Logarithm

The first step in solving a natural logarithmic equation is to isolate the logarithm by moving any constants or variables outside of the logarithm to the other side of the equation. This step is crucial in order to simplify the equation and make it easier to solve.

For instance, in the equation ln(x) + 3 = 2, the constant 3 would be moved to the right side, resulting in ln(x) = -1.

### Step 2: Use the Exponential Function

Since the natural logarithm is the inverse of the natural growth function, the exponential function can be used to eliminate the logarithm. By raising both sides of the equation to the power of e, the equation becomes more manageable.

For our example, e^(ln(x)) is equivalent to x, and e^(-1) equals approximately 0.37. Therefore, our equation would now become x = 0.37.

### Step 3: Simplify and Solve for x

Using the property that e^(ln(x)) equals x, we can simplify the equation to just x. This leaves us with x = e^(-1). To find the numerical value of x, a calculator can be used or the value of e^(-1) can be approximated to 0.37. Hence, the solution to the original equation is x = 0.37.

## Converting Logarithmic Functions to Natural Logarithmic Functions

Oftentimes, a logarithmic function may not be in its natural form, such as log4(x). If the need arises to convert the function to its natural form, the Proportion Rule for logarithms can be utilized.

The Proportion Rule states that loga(x) equals ln(x)/ln(a). Therefore, for our example, we would have ln(x)/ln(4). Simplifying this expression results in ln(x)/ln(e^2), which becomes ln(x)/2, or ln(square root of x).

In summary, solving natural logarithmic equations requires isolating the logarithm, applying the exponential function, and simplifying to find the numerical solution for x. And if a logarithmic function needs to be converted to its natural form, the Proportion Rule can be an effective tool for doing so.