Numerical Calculus Tool

Derivative at a Point Calculator

Calculate the derivative f'(x) of a function at a specific x value. Enter standard mathematical expressions such as x^2 + 2x, 3x^2 - 4x + 1, 2(x+1), or sin(x).

Calculate the Derivative at a Point

Enter a function of x and the point where you want to calculate its derivative. The calculator uses numerical differentiation.

Examples: x^2 + 2x, 3x^2 - 4x + 1, 2(x+1), sin(x).

Enter Functions With or Without the * Symbol

This calculator accepts common mathematical notation with implicit multiplication. You do not need to write an asterisk between a coefficient and x.

2x Automatically interpreted as 2 × x.
3x² Enter this as 3x^2.
2(x + 1) Parentheses can directly follow a coefficient.
x(x + 1) A variable can directly precede parentheses.
2sin(x) A coefficient can directly precede a function.
xcos(x) A variable can directly precede a function.

Example Expressions

x^2 + 2x
3x^2 - 4x + 1
2(x+1)
x(x-3)
2sin(x)

What Is a Derivative at a Point?

The derivative of a function measures its instantaneous rate of change. For a function f(x), the derivative is written as f'(x).

When the derivative is evaluated at a particular value x = a, it gives the instantaneous slope of the function at that point.

\[ f'(a) = \lim_{h \to 0} \frac{ f(a+h)-f(a) }{h} \]

Geometrically, the derivative at a point is the slope of the tangent line to the function at that point.

How This Derivative Calculator Works

This page calculates the derivative numerically rather than symbolically. It uses a central-difference approximation.

\[ f'(x) \approx \frac{ f(x+h)-f(x-h) }{ 2h } \]

A small value of h is used to estimate the slope from function values immediately to the left and right of the selected point.

Function The mathematical expression f(x) that you enter.
Point The x value where the derivative is required.
Step Size A small numerical h value is used for the approximation.
Result The estimated instantaneous slope at the selected point.

Derivative at a Point Examples

Example 1: x² + 2x

Enter:

x^2 + 2x

Then choose an x value such as:

x = 3

Example 2: 3x² − 4x + 1

3x^2 - 4x + 1

Example 3: 2(x + 1)

2(x+1)

Example 4: sin(x)

sin(x)

Example 5: Exponential Function

exp(x)

Supported Mathematical Functions

Polynomial Functions x^2, x^3 + 2x, 3x^2 − 4x + 1
Implicit Multiplication 2x, 3x^2, 2(x+1), x(x+1)
Trigonometric Functions sin(x), cos(x), tan(x)
Exponential Functions exp(x)
Natural Logarithm ln(x)

Applications of Derivatives

Derivatives are used throughout mathematics, science, engineering, economics and data analysis to describe rates of change.

For more advanced problems, you can also use the Critical Point Calculator or Higher-Order Derivative Calculator .

Related Derivative Calculators

Summe.org provides several derivative and calculus tools for different types of problems.

Multivariable Calculus Tools

When a function contains multiple variables, Summe.org also provides tools for gradients, directional derivatives and other multivariable calculus operations.

Derivatives and Integrals

Derivatives and integrals are two fundamental operations in calculus. Differentiation studies rates of change, while integration studies accumulation and area.

The Fundamental Theorem of Calculus establishes an important connection between these operations.

Frequently Asked Questions

Can I enter x^2 + 2x without the * symbol?

Yes. The calculator automatically interprets 2x as 2*x. Therefore, both x^2 + 2x and x^2 + 2*x are accepted.

Can I enter 3x^2?

Yes. The calculator recognizes the implicit multiplication between 3 and x, so 3x^2 is accepted.

Can I enter 2(x+1)?

Yes. The calculator converts the implicit multiplication into the equivalent expression 2*(x+1).

Can I enter x(x+1)?

Yes. Expressions such as x(x+1) are supported.

What does the derivative at a point represent?

The derivative at a point represents the instantaneous rate of change of the function and, geometrically, the slope of its tangent line at that point.

Is this a symbolic derivative calculator?

No. This particular tool calculates the derivative numerically at a selected point. If you need the symbolic derivative of an entire function, use the Derivative Calculator .

What numerical method is used?

The calculator uses a central-difference approximation: [f(x+h) − f(x−h)] / (2h), with a small numerical step size.

Can I calculate the derivative of sin(x)?

Yes. Enter sin(x) and specify the x value where you want the numerical derivative.

What happens if the function is undefined at the selected point?

The calculator will return an error if the function cannot be evaluated at the selected point or at one of the nearby points used for the numerical approximation.

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