Last updated on July 18th, 2025
We use the derivative of ln(x), which is 1/x, as a tool for understanding how the natural logarithm function changes in response to a slight change in x. Derivatives help us calculate profit or loss in real-life situations. We will now discuss the derivative of ln(x) in detail.
We now understand the derivative of ln(x). It is commonly represented as d/dx (ln(x)) or (ln(x))', and its value is 1/x. The function ln(x) has a clearly defined derivative, indicating it is differentiable within its domain. The key concepts are mentioned below: Natural Logarithm Function: ln(x) is the logarithm to the base e. Chain Rule: Rule for differentiating functions involving ln(x). Reciprocal Function: 1/x is the derivative of ln(x).
The derivative of ln(x) can be denoted as d/dx (ln(x)) or (ln(x))'. The formula we use to differentiate ln(x) is: d/dx (ln(x)) = 1/x The formula applies to all x > 0.
We can derive the derivative of ln(x) using proofs. To show this, we will use the properties of logarithms along with the rules of differentiation. There are several methods we use to prove this, such as: By First Principle Using Chain Rule Using Properties of Logarithms We will now demonstrate that the differentiation of ln(x) results in 1/x using the above-mentioned methods: By First Principle The derivative of ln(x) can be proved using the First Principle, which expresses the derivative as the limit of the difference quotient. To find the derivative of ln(x) using the first principle, we will consider f(x) = ln(x). Its derivative can be expressed as the following limit. f'(x) = limₕ→₀ [f(x + h) - f(x)] / h … (1) Given that f(x) = ln(x), we write f(x + h) = ln(x + h). Substituting these into equation (1), f'(x) = limₕ→₀ [ln(x + h) - ln(x)] / h = limₕ→₀ [ln((x + h)/x)] / h = limₕ→₀ [ln(1 + h/x)] / h By using the property ln(1 + u) ≈ u for small u, = limₕ→₀ [h/x] / h = limₕ→₀ 1/x Hence, f'(x) = 1/x. Thus, proved. Using Chain Rule To prove the differentiation of ln(x) using the chain rule, We use the formula: ln(x) = logₑ(x) Consider f(x) = x and g(x) = x So we get, ln(x) = ln(f(x)) By chain rule: d/dx [ln(f(x))] = f'(x)/f(x) … (1) Let’s substitute f(x) = x in equation (1), d/dx (ln(x)) = 1/x Thus, the derivative of ln(x) is 1/x. Using Properties of Logarithms We will now prove the derivative of ln(x) using the properties of logarithms. The step-by-step process is demonstrated below: Here, we use the property, ln(x) = logₑ(x) Given that, u = x and v = e Using the property: d/dx [ln(x)] = 1/x Hence, d/dx (ln(x)) = 1/x.
When a function is differentiated several times, the derivatives obtained are referred to as higher-order derivatives. Higher-order derivatives can be a little tricky. To understand them better, think of a car where the speed changes (first derivative) and the rate at which the speed changes (second derivative) also changes. Higher-order derivatives make it easier to understand functions like ln(x). For the first derivative of a function, we write f′(x), which indicates how the function changes or its slope at a certain point. The second derivative is derived from the first derivative, which is denoted using f′′(x). Similarly, the third derivative, f′′′(x), is the result of the second derivative, and this pattern continues. For the nth Derivative of ln(x), we generally use fⁿ(x) for the nth derivative of a function f(x), which tells us the change in the rate of change (continuing for higher-order derivatives).
When x is 0, the derivative is undefined because ln(x) is not defined for x ≤ 0. When x = 1, the derivative of ln(x) = 1/1, which is 1.
Students frequently make mistakes when differentiating ln(x). These mistakes can be resolved by understanding the proper solutions. Here are a few common mistakes and ways to solve them:
Calculate the derivative of ln(x²).
Here, we have f(x) = ln(x²). Using the chain rule, f'(x) = d/dx [ln(g(x))] g(x) = x² g'(x) = 2x f'(x) = g'(x)/g(x) f'(x) = 2x/x² f'(x) = 2/x Thus, the derivative of ln(x²) is 2/x.
We find the derivative of the given function by recognizing it as a composite function and applying the chain rule. We differentiate the inner function and then use the chain rule to get the final result.
A company uses a natural logarithm to model its growth rate, represented by the function y = ln(x), where y represents the growth rate and x is time in years. Calculate the rate of change of growth when x = 3 years.
We have y = ln(x) (growth rate)...(1) Now, we will differentiate the equation (1) Take the derivative of ln(x): dy/dx = 1/x Given x = 3 (substitute this into the derivative) dy/dx = 1/3 Hence, the rate of change of growth at x = 3 years is 1/3.
We find the rate of change of growth at x = 3 years as 1/3, which means that at this point, the growth rate increases at a rate of 1/3 per year.
Derive the second derivative of the function y = ln(x).
The first step is to find the first derivative, dy/dx = 1/x...(1) Now we will differentiate equation (1) to get the second derivative: d²y/dx² = d/dx [1/x] d²y/dx² = -1/x² Therefore, the second derivative of the function y = ln(x) is -1/x².
We use the step-by-step process, where we start with the first derivative. We then differentiate 1/x, applying the power rule to find the final answer.
Prove: d/dx (ln(x³)) = 3/x.
Let’s start using the chain rule: Consider y = ln(x³) = 3 ln(x) To differentiate, we use the chain rule: dy/dx = 3 d/dx [ln(x)] Since the derivative of ln(x) is 1/x, dy/dx = 3 (1/x) dy/dx = 3/x Hence proved.
In this step-by-step process, we used the chain rule to differentiate the equation. We rewrite ln(x³) using properties of logarithms and then differentiate to derive the equation.
Solve: d/dx (ln(x)/x)
To differentiate the function, we use the quotient rule: d/dx (ln(x)/x) = (d/dx (ln(x)) · x - ln(x) · d/dx(x))/x² We will substitute d/dx (ln(x)) = 1/x and d/dx (x) = 1 = (1/x · x - ln(x) · 1) / x² = (1 - ln(x)) / x² Therefore, d/dx (ln(x)/x) = (1 - ln(x)) / x²
In this process, we differentiate the given function using the quotient rule. As a final step, we simplify the equation to obtain the final result.
Derivative: The derivative of a function indicates how the given function changes in response to a slight change in x. Natural Logarithm: The natural logarithm is the logarithm to the base e, represented as ln(x). Chain Rule: A fundamental rule in calculus for differentiating compositions of functions. First Derivative: The initial result of a function, which gives us the rate of change of a specific function. Quotient Rule: A method used to find the derivative of the division of two functions. ```
Jaskaran Singh Saluja is a math wizard with nearly three years of experience as a math teacher. His expertise is in algebra, so he can make algebra classes interesting by turning tricky equations into simple puzzles.
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