Linear Approximation Calculator

To use the linear approximation calculator, choose the type of your function, enter the function, input the point at which you want to find the approximation, and click Calculate.


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Linear Approximation Calculator 

Find the closest approximation in the form of a line of implicit, explicit, polar, or parametric functions using a linear approximation calculator. Also, get the step-by-step solution that explains the calculation in the results.

What is linear approximation?

Linear approximation is a method in calculus in which a function is approximated by a linear function near a specific point. Instead of dealing with the function's complex behavior everywhere, we study its behavior at a specific point where it can be approximated as a straight line.

For a function f(x) that's differentiable at point a, the function can be approximated by a tangent line at that point. This tangent line, being linear, provides a simpler approximation for the function near a.

The formula for linear approximation:

The mathematical representation of the linear approximation L(x) of a function f(x) near a point a is:

L(x) = f(a)+f’ (a)(x−a)


  • L(x) is the linear approximation.
  • f(a) denotes the value of the function at point a. 
  • f’(a) is the derivative of the function at point a, representing the slope of the tangent line at that point.

In this formula, f(a) ensures that the linear approximation and the function coincide at x = a, while the term f’ (a)(x−a) accounts for the change based on how x deviates from "a", all scaled by the rate of change at a.

How to find the linear approximation?

To solidify understanding, let's see a concrete example:


Approximate the function f(x) = x near the point x = 4 using linear approximation.


  1. Compute the function value at x=4:

f(4) = √4 =2.

  1. Determine the derivative:

The derivative of f(x) is f’ (x) = 1/(2√x). Evaluating at x = 4 gives:

f’ (4) = 1/(2√4) = ¼ .

  1. Apply the linear approximation formula:

Using the formula, we find:

L(x) = 2+ ¼ (x−4)

Simplifying, we get:

L(x) = ¼ x + 1

Thus, in the vicinity of x=4, the function f(x)= x can be approximated by the linear function 

L(x) = ¼ x + 1.

Application of linear approximation:

While its foundational principles lie in advanced mathematics, the practical applications of linear approximation are present in our everyday lives in ways we often take for granted. Here's a look at some of its applications and uses in daily life:

Engineering and Architecture: When constructing bridges, tunnels, or buildings, engineers often use linear approximations to simplify complex equations related to material stress, load distribution, or other architectural challenges.

Even slight changes in weight or pressure can be predicted using linear approximations.

Meteorology: Weather forecasting involves a lot of differential equations. For slight changes in time intervals, linear approximations can predict small weather changes, aiding in short-term forecasts.

Computer Graphics: When rendering graphics, especially in video games or simulations, linear approximations help in shading, reflections, and other visual effects, giving users a more realistic experience.

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