Directional Derivative Calculator

The Directional Derivative Calculator is the best online tool for finding the directional derivative of a function in multidimensional space quickly and accurately.

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Table of Contents:

Introduction to Directional Derivative Calculator:

Directional derivative calculator angle is the best online source that helps you to find the directional derivative of a given function in multidimensional space. Our tool determines the rate of a change of function at a specific point.

Directional Derivative Calculator with Steps

The directional derivative at a point calculator is a handy tool for students, teachers, professionals, or researchers who want to get a solution of multivariable function in a specific direction of scalar field.

What is a Directional Derivative?

The directional derivative is a process that is used to find the multivariable function f(x, y, z,…) at a point a = (a1, a2, a3,…) to measure the rate at which the given function changes, going towards a in the direction of a vector u = (u1, u2, u3,…).

The directional derivative process is used for partial derivative functions where you can find the scalar function in a particular direction. As it determines the maximum or minimum value of several functions along the given direction that describes function behavior in a scalar field.

Formula of Directional Derivative:

The directional derivative is mathematically defined as a multivariable function f, of a given function at point a in the direction of vector u. The directional derivative formula used by the directional derivative calculator with angle is given as:

$$ D_u f(a) \;=\; \nabla f(a) . u $$

  • Du: the directional derivative toward the u vector
  • f(a): function at a point a
  • ▽: the gradient of a multivariable function
  • Here, the gradient ▽ of a function f at a point a is f(a).

$$ \nabla f(a) \;=\; \left( \frac{\partial f}{\partial x_1}(a),\; \frac{\partial f}{\partial x_2}(a),\; \frac{\partial f}{\partial x_3}(a), … \right) $$

How to Calculate Directional Derivative?

The directional derivative online calculator is an easy way to calculate the partial derivation in a specific direction of scalar field. The process of direction derivative calculation is given as:

Step 1:

Identify the given function f(x, y, z…) and a specific point value a(a1, a2,..) along the u direction.

Step 2:

Evaluate the gradient ▽ of a given function as it takes the partial differential with respect to its variable along the direction.

Step 3:

After differentiation, simplify the expression and then apply the value of point a(a1, a2,..)

Step 4:

After putting the point value in the differentiation function simplify it to get the solution.

Solved Example of Directional Derivative:

The directional derivative calculator angle solves the directional derivative problem without any hurdle. So, here’s an example to let you know how it actually calculates,

Example:

Determine the directional derivative of the following,

$$ f(x,y) \;=\; x^2 - xy + 3y^2\; in\; the\; direction\; of\; \vec{u} \;=\; (cos\; \theta) \hat{i} + (sin\; \theta) \hat{j} $$

Solution:

Identify the given function f(x, y, z…) at a particular point and direction,

$$ f(x,y) \;=\; x^2 - xy + 3y^2 $$

$$ \vec{u} \;=\; (cos\; \theta) \hat{i} + (sin\; \theta) \hat{j} $$

Compute the gradient of the function:

$$ D_{\vec{u}} f(x, y, z) \;=\; f_x (x,y) cos\; \theta + f_y (x,y) sin\; \theta $$

$$ \;=\; (2x - y) \frac{3}{5} + (-x + 6y) \frac{4}{5} $$

$$ =\; \frac{6x}{5} - \frac{3y}{5} - \frac{4x}{5} + \frac{24y}{5} $$

$$ =\; \frac{2x + 21y}{5} $$

Put the value of given point a in the above function and simply use the expression to get the solution,

$$ D_{\vec{u}} f(1,2) \;=\; \frac{2(-1) + 21(2)}{5} \;=\; \frac{-2 + 42}{5} \;=\; 8 $$

How to Use Directional Derivative Calculator?

The directional derivative at a point calculator has a simple design that makes it easy for you to use it for the evaluation of directional derivative problems. Follow some simple steps that are given as:

  • Enter the given function in the given input field that you want to differentiate with a specific point.
  • Put the value of the direction of a vector u(u1, u2,..) in the next input field.
  • Put the value of the point around which the directional derivative is evaluated.
  • Check the given directional derivative function value before clicking the calculate button of the directional derivative online calculator.
  • Click the “Calculate” button to get the result of your directional derivative problem.
  • If you are trying our tool for the first time then you can use the load example option to learn more about this process.
  • The “Recalculate” button brings you back to the home page where you can find more solutions of directional derivative problems.

Results from Directional Derivative at a Point Calculator:

The directional derivative calculator with angle gives you the solution from a given function when you give it an input. It includes as:

  • Result Option:

When you click on the result option, it gives you a solution of partial differential function in a specific point.

  • Possible Steps:

When you click on it, this option will provide you step by step solution where you get the function in the direction of u.

  • Plot Option:

It will give you a graphical representation of directional derivative function to get a better understanding of the result.

Advantages of Directional Derivative Online Calculator:

The directional derivative at a point calculator provides tons of advantages and helps you to calculate the directional derivative of a function. These advantages are:

  • It is a free-of-cost tool so you can use it for free to find directional derivative problems with solutions.
  • It gives you conceptual clarity for directional derivative process when you use it to solve multiple examples.
  • It saves the time and effort that you consume when calculating complex directional derivative functions to find the maximum or minimum value manually.
  • It is an adaptable tool that provides you accurate solutions whenever you use it to calculate directional derivatives.
  • Our directional derivative calculator angle enables you to use it multiple times for the evaluation of directional derivative problems.
  • It is a handy tool so you can access it through an online platform from anywhere.
Related References
Frequently Ask Questions

Is directional derivative a scalar or vector?

The directional derivative is not a vector but it is a scalar quantity because it represents the rate of change of the function f in a particular direction at a specific point a. It gives a numerical value that denotes the function's slope in that direction, rather than a vector quantity. That is why both the magnitude and direction are changed.

When is directional derivative zero?

The directional derivative of a function f is zero, If the function f is constant, then its directional derivative in any direction at any point will be zero. Secondly, at points where the gradient ∇f(a)of f is zero, the directional derivative of f in any direction will also be zero. Third, when the function is along curves where f(x)=c, the directional derivative of f in the direction tangent to the curve will be zero, which means the function f does not change its value.

Therefore, the directional derivative of a function f is zero when the function is constant, when its gradient is zero at a point, or along curves where the function has constant values.

Can the directional derivative be negative?

Yes, the directional derivative of a function f can be negative. It has multiple reasons which are given as:

  • If function f decreases in the vector direction at point a, then D_vf(a) will be negative.
  • The sign of the directional derivative also depends on the angle between the gradient vector ∇f(a) and the direction vector v.

If ∇f(a) ⋅ v < 0, then D_vf(a) < 0

If ∇f(a) ⋅ v > 0, then D_vf(a) > 0

  • When the function f decreases along the curve, the directional derivative can be negative.

Do directional derivatives require a unit vector?

Directional derivatives do not always require a unit vector, but the unit vectors ensure the rate of change of function remains in the direction of a given vector or if its magnitude changes its direction remains the same. You can define the directional derivative with any nonzero vector v.Therefore, it is common to express directional derivatives in terms of unit vectors.

Does the directional derivate equal the magnitude of the gradient?

No, the directional derivative of a function f in the direction of a vector v at a point a does not necessarily equal the magnitude of the gradient.

The directional derivative D_vf(a) of a function f is given by:

$$ D_{vf}(a) \;=\; \nabla \frac{f(a) ⋅ v}{∥v∥} $$

Therefore, while the magnitude ∥∇f(a)∥ is related to the directional derivative D_vf(a), they are not equal unless v is in the same direction as, $$ \nabla f(a) cos⁡(θ) \;=\; 1 $$

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