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Last updated on September 9, 2025

Derivative of x²/2

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We use the derivative of x²/2, which is x, as a measuring tool for how the 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 x²/2 in detail.

Derivative of x²/2 for US Students
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What is the Derivative of x²/2?

We now understand the derivative of x²/2.

It is commonly represented as d/dx (x²/2) or (x²/2)', and its value is x.

The function x²/2 has a clearly defined derivative, indicating it is differentiable within its domain.

The key concepts are mentioned below:

Power Function: (x²/2 is a polynomial function).

Power Rule: Rule for differentiating x²/2.

Constant Multiple Rule: The derivative of a constant times a function.

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Derivative of x²/2 Formula

The derivative of x²/2 can be denoted as d/dx (x²/2) or (x²/2)'. The formula we use to differentiate x²/2 is: d/dx (x²/2) = x (x²/2)' = x The formula applies to all x.

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Proofs of the Derivative of x²/2

We can derive the derivative of x²/2 using proofs.

To show this, we will use the rules of differentiation.

There are several methods we use to prove this, such as:

By First Principle

Using Power Rule

Using Constant Multiple Rule

We will now demonstrate that the differentiation of x²/2 results in x using the above-mentioned methods:

 

By First Principle

The derivative of x²/2 can be proved using the First Principle, which expresses the derivative as the limit of the difference quotient.

To find the derivative of x²/2 using the first principle, we will consider f(x) = x²/2.

Its derivative can be expressed as the following limit. f'(x) = limₕ→₀ [f(x + h) - f(x)] / h … (1)

Given that f(x) = x²/2, we write f(x + h) = (x + h)²/2.

Substituting these into equation (1), f'(x) = limₕ→₀ [(x + h)²/2 - x²/2] / h = limₕ→₀ [(x² + 2xh + h²)/2 - x²/2] / h = limₕ→₀ [2xh + h²]/2h = limₕ→₀ [x + h/2] As h approaches 0, f'(x) = x.

Hence, proved.

 

Using Power Rule

To prove the differentiation of x²/2 using the power rule, We use the formula: d/dx (xⁿ) = n*xⁿ⁻¹

For x², n = 2.

So, d/dx (x²) = 2*x¹ = 2x. Since we have x²/2, d/dx (x²/2) = (1/2)*d/dx (x²) = (1/2)*2x = x.

 

Using Constant Multiple Rule

We will now prove the derivative of x²/2 using the constant multiple rule.

The formula we use is: d/dx (c*f(x)) = c*d/dx (f(x))

Let c = 1/2 and f(x) = x².

So, d/dx (x²/2) = (1/2)*d/dx (x²) = (1/2)*2x = x.

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Higher-Order Derivatives of x²/2

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 x²/2.

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 x²/2, 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).

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Special Cases:

When x is 0, the derivative of x²/2 = 0, which means there is no change at this point. When x is negative, the derivative of x²/2 is negative, indicating a downward slope.

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Common Mistakes and How to Avoid Them in Derivatives of x²/2

Students frequently make mistakes when differentiating x²/2. These mistakes can be resolved by understanding the proper solutions. Here are a few common mistakes and ways to solve them:

Mistake 1

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Not simplifying the equation

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Students may forget to simplify the equation, which can lead to incomplete or incorrect results. They often skip steps and directly arrive at the result, especially when solving using the product or chain rule. Ensure that each step is written in order. Students might think it is awkward, but it is important to avoid errors in the process.

Mistake 2

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Forgetting the Constant Multiple

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They might not remember that x²/2 includes a constant multiple. Keep in mind that you should consider the constant factor when differentiating. It will help you understand that the constant affects the derivative.

Mistake 3

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Incorrect use of Power Rule

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While differentiating functions such as x²/2, students misapply the power rule.

 

For example: Incorrect differentiation: d/dx (x²/2) = 2x/2 = x/2.

Ensure that the constant is properly handled: d/dx (x²/2) = (1/2)*d/dx (x²) = x.

Mistake 4

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Not writing Constants and Coefficients

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There is a common mistake that students at times forget to multiply the constants placed before the function.

 

For example, they incorrectly write d/dx (5x²/2) = x.

Students should check the constants in the terms and ensure they are multiplied properly.

 

For e.g., the correct equation is d/dx (5x²/2) = 5x.

Mistake 5

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Not Applying the Power Rule

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Students often forget to use the power rule. This happens when the exponent of a polynomial is not considered.

 

For example: Incorrect: d/dx (x³/2) = x.

To fix this error, students should apply the power rule properly: d/dx (x³/2) = (1/2)*3x² = (3/2)x².

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Examples Using the Derivative of x²/2

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Problem 1

Calculate the derivative of (x²/2)·x³.

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Here, we have f(x) = (x²/2)·x³.

Using the product rule, f'(x) = u′v + uv′

In the given equation, u = x²/2 and v = x³.

Let’s differentiate each term, u′= d/dx (x²/2) = x v′= d/dx (x³) = 3x²

Substituting into the given equation, f'(x) = (x)·(x³) + (x²/2)·(3x²)

Let’s simplify terms to get the final answer, f'(x) = x⁴ + (3/2)x⁴ = (5/2)x⁴

Thus, the derivative of the specified function is (5/2)x⁴.

Explanation

We find the derivative of the given function by dividing the function into two parts. The first step is finding its derivative and then combining them using the product rule to get the final result.

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Problem 2

A construction company is laying a pipeline represented by the function y = x²/2 where y represents the elevation at a distance x. If x = 1 meter, measure the slope of the pipeline.

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We have y = x²/2 (slope of the pipeline)...(1)

Now, we will differentiate the equation (1)

Take the derivative of x²/2: dy/dx = x

Given x = 1 (substitute this into the derivative) dy/dx = 1

Hence, we get the slope of the pipeline at a distance x = 1 as 1.

Explanation

We find the slope of the pipeline at x = 1 as 1, which means that at a given point, the height of the pipeline would rise at a rate equal to the horizontal distance.

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Problem 3

Derive the second derivative of the function y = x²/2.

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The first step is to find the first derivative, dy/dx = x...(1)

Now we will differentiate equation (1) to get the second derivative: d²y/dx² = d/dx (x) d²y/dx² = 1

Therefore, the second derivative of the function y = x²/2 is 1.

Explanation

We use the step-by-step process, where we start with the first derivative. We then differentiate x to find the second derivative, which is a constant 1.

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Problem 4

Prove: d/dx ((3x²)/2) = 3x.

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Let’s start using the constant multiple rule:

Consider y = (3x²)/2

To differentiate, we use the constant multiple rule: dy/dx = (3/2)*d/dx (x²)

Since the derivative of x² is 2x, dy/dx = (3/2)*2x dy/dx = 3x

Hence proved.

Explanation

In this step-by-step process, we used the constant multiple rule to differentiate the equation. Then, we replace x² with its derivative. As a final step, we simplify to derive the equation.

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Problem 5

Solve: d/dx ((x²/2)/x)

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To differentiate the function, we use the quotient rule: d/dx ((x²/2)/x) = (d/dx (x²/2)·x - (x²/2)·d/dx(x))/x²

We will substitute d/dx (x²/2) = x and d/dx (x) = 1 (x·x - (x²/2)·1) / x² = (x² - x²/2) / x² = (2x²/2 - x²/2) / x² = (x²/2) / x² = 1/2

Therefore, d/dx ((x²/2)/x) = 1/2.

Explanation

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.

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FAQs on the Derivative of x²/2

1.Find the derivative of x²/2.

Using the power rule, d/dx (x²/2) = x (simplified).

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2.Can we use the derivative of x²/2 in real life?

Yes, we can use the derivative of x²/2 in real life in calculating the rate of change of any motion, especially in fields such as mathematics, physics, and economics.

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3.Is it possible to take the derivative of x²/2 at the point where x = 0?

Yes, the derivative at x = 0 is 0, indicating no change at this point.

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4.What rule is used to differentiate (x²/2)/x?

We use the quotient rule to differentiate (x²/2)/x, d/dx ((x²/2)/x) = (x·x - (x²/2)·1) / x² = 1/2.

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5.Are the derivatives of x²/2 and (x²/2)² the same?

No, they are different. The derivative of x²/2 is equal to x, while the derivative of (x²/2)² is x³/2.

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Important Glossaries for the Derivative of x²/2

  • Derivative: The derivative of a function indicates how the given function changes in response to a slight change in x.

 

  • Power Rule: A differentiation rule used to find the derivative of a power function.

 

  • Constant Multiple Rule: A rule stating that the derivative of a constant times a function is the constant times the derivative of the function.

 

  • First Derivative: The initial result of differentiating a function, indicating the rate of change of the function.

 

  • Quotient Rule: A rule used to differentiate functions that are divided by each other.
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Jaskaran Singh Saluja

About the Author

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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Fun Fact

: He loves to play the quiz with kids through algebra to make kids love it.

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