Last updated on July 18th, 2025
We use the derivative of ln(2/x), which is -1/x, as a measuring tool for how the logarithmic function changes in response to a slight change in x. Derivatives help us calculate profit or loss in real-life situations. We will now talk about the derivative of ln(2/x) in detail.
We now understand the derivative of ln(2/x). It is commonly represented as d/dx [ln(2/x)] or [ln(2/x)]', and its value is -1/x. The function ln(2/x) has a clearly defined derivative, indicating it is differentiable within its domain.
The key concepts are mentioned below:
Logarithmic Function: ln(x) represents the natural logarithm of x.
Chain Rule: Rule for differentiating ln(2/x) (since it involves a composition of functions).
Reciprocal Rule: Involves differentiating 1/x.
The derivative of ln(2/x) can be denoted as d/dx [ln(2/x)] or [ln(2/x)]'.
The formula we use to differentiate ln(2/x) is: d/dx [ln(2/x)] = -1/x (or) [ln(2/x)]' = -1/x
The formula applies to all x where x > 0.
We can derive the derivative of ln(2/x) using proofs. To show this, we will use logarithmic identities along with the rules of differentiation. There are several methods we use to prove this, such as:
We will now demonstrate that the differentiation of ln(2/x) results in -1/x using the above-mentioned methods:
The derivative of ln(2/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(2/x) using the first principle, we will consider f(x) = ln(2/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(2/x), we write f(x + h) = ln(2/(x + h)).
Substituting these into equation (1), f'(x) = limₕ→₀ [ln(2/(x + h)) - ln(2/x)] / h = limₕ→₀ [ln((2/x) / (2/(x + h)))] / h = limₕ→₀ [ln((x + h)/x)] / h
We now use the logarithmic property ln(a/b) = ln(a) - ln(b). f'(x) = limₕ→₀ [ln(1 + h/x)] / h
Using the limit property ln(1 + u) ≈ u when u is small, f'(x) = limₕ→₀ (h/x) / h = limₕ→₀ 1/x f'(x) = -1/x
Hence, proved.
To prove the differentiation of ln(2/x) using the chain rule, We use the formula: ln(2/x) = ln(2) - ln(x)
The derivative of ln(x) is 1/x, and the constant ln(2) differentiates to 0. d/dx [ln(2/x)] = d/dx [ln(2) - ln(x)] d/dx [ln(2)] = 0 and d/dx [-ln(x)] = -1/x Therefore, d/dx [ln(2/x)] = -1/x
We will now prove the derivative of ln(2/x) using the quotient rule. The step-by-step process is demonstrated below: Here, we use the formula, ln(2/x) = ln(2) - ln(x)
The derivative of a constant is 0, and the derivative of ln(x) is 1/x. Using these rules: d/dx [ln(2/x)] = d/dx [ln(2) - ln(x)]
Since d/dx [ln(2)] = 0, d/dx [-ln(x)] = -1/x Thus: d/dx [ln(2/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(2/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(2/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 = 0, the derivative is undefined because ln(2/x) is undefined there. When x = 1, the derivative of ln(2/x) = -1/1, which is -1.
Students frequently make mistakes when differentiating ln(2/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(3/x).
Here, we have f(x) = ln(3/x).
Using the chain rule, f'(x) = d/dx [ln(3) - ln(x)]
The derivative of a constant is 0, and the derivative of ln(x) is 1/x. Thus, f'(x) = -1/x
Therefore, the derivative of ln(3/x) is -1/x.
We find the derivative of the given function by applying the chain rule and considering the properties of logarithms. The first step is finding its derivative and then simplifying to get the final result.
The growth rate of a plant is modeled by the function y = ln(2/x) where y represents the growth rate at time x. If x = 2 weeks, find the growth rate.
We have y = ln(2/x) (growth rate of the plant)...(1)
Now, we will differentiate the equation (1)
Take the derivative ln(2/x): dy/dx = -1/x Given x = 2 (substitute this into the derivative) dy/dx = -1/2
Hence, the growth rate at time x = 2 weeks is -1/2.
We find the growth rate at x = 2 weeks as -1/2, which means that at this point in time, the growth rate of the plant decreases at a rate of -1/2.
Derive the second derivative of the function y = ln(4/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]
Here we use the power rule, d²y/dx² = 1/x²
Therefore, the second derivative of the function y = ln(4/x) is 1/x².
We use the step-by-step process, where we start with the first derivative. Using the power rule, we differentiate -1/x. We then simplify the terms to find the final answer.
Prove: d/dx [ln(5/x)] = -1/x.
Let’s start using the chain rule: Consider y = ln(5/x) ln(5) - ln(x)
To differentiate, we use the chain rule: dy/dx = d/dx [ln(5)] - d/dx [ln(x)]
Since the derivative of ln(x) is 1/x and ln(5) is a constant, dy/dx = 0 - 1/x
Substituting y = ln(5/x), d/dx [ln(5/x)] = -1/x
Hence proved.
In this step-by-step process, we used the chain rule to differentiate the equation.
Then, we replace ln(x) with its derivative.
As a final step, we substitute y = ln(5/x) to derive the equation.
Solve: d/dx [ln(x/2)]
To differentiate the function, we use the chain rule: d/dx [ln(x/2)] = d/dx [ln(x) - ln(2)]
The derivative of a constant is 0, and the derivative of ln(x) is 1/x.
Thus, d/dx [ln(x/2)] = 1/x
Therefore, d/dx [ln(x/2)] = 1/x
In this process, we differentiate the given function using the chain rule and properties of logarithms. As a final step, we simplify the equation to obtain the final result.
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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