Proving the Vector Calculus Identity: (1/g^2)(g∇f - f∇g)

Thread starter Rubik
Start date Sep 21, 2011
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Calculus Identity Vector Vector calculus

In summary, the Vector Calculus Identity is a fundamental theorem in vector calculus that relates the integral of a vector field over a closed curve to the values of the vector field at the endpoints of the curve. It is used in many areas of physics and engineering, including electromagnetism, fluid dynamics, and mechanics. It has practical applications in computer graphics, computer vision, geology, meteorology, economics, finance, and biology. Common mistakes when applying the Vector Calculus Identity include using the wrong form, not properly defining the closed curve or surface, not considering direction and orientation, and not accounting for boundary conditions or constraints. It is important to carefully follow the steps of the identity to avoid these and other errors.

Sep 21, 2011

Rubik

I am trying to figure out a proof for this identity

[itex]\nabla[/itex](f/g) = (1/g²) (g[itex]\nabla[/itex]f - f[itex]\nabla[/itex]g)

Any ideas?

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Sep 21, 2011

mathman

Science Advisor

It looks like a vector version of the derivative of a quotient. Look at each component separately.

Sep 21, 2011

techmologist

The quotient rule for ordinary derivatives:

(f/g)' = (gf' - fg')/g²

works for partial derivatives, too.

Sep 21, 2011

Rubik

Thanks so much I got it :)

What is the Vector Calculus Identity?

The Vector Calculus Identity, also known as the Fundamental Theorem of Calculus for Vector Fields, is a mathematical formula that relates the integral of a vector field over a closed curve to the values of the vector field at the endpoints of the curve. It is an important concept in vector calculus and is used in many areas of physics and engineering.

What is the difference between the Gradient Theorem and the Divergence Theorem?

The Gradient Theorem and the Divergence Theorem are both special cases of the Vector Calculus Identity. The Gradient Theorem relates the integral of a vector field over a smooth curve to the values of the vector field at the endpoints of the curve. The Divergence Theorem relates the integral of a vector field over a closed surface to the values of the vector field on the boundary of the surface. In other words, the Gradient Theorem applies to curves while the Divergence Theorem applies to surfaces.

How is the Vector Calculus Identity used in physics?

The Vector Calculus Identity is used in many areas of physics, including electromagnetism, fluid dynamics, and mechanics. In electromagnetism, it is used to calculate the work done by an electric or magnetic field on a charged particle moving along a closed path. In fluid dynamics, it is used to calculate the flow of a fluid through a closed surface. In mechanics, it is used to calculate the work done by a force on an object moving along a path.

What are some real-world applications of the Vector Calculus Identity?

The Vector Calculus Identity has many practical applications in engineering and science. It is used in computer graphics to simulate fluid dynamics and in computer vision to track the motion of objects. It is also used in geology to map the flow of underground fluids and in meteorology to model weather patterns. Additionally, it is used in economics and finance to model the flow of money and in biology to study the movement of fluids in living organisms.

What are some common mistakes made when applying the Vector Calculus Identity?

One common mistake is using the wrong form of the Vector Calculus Identity for the given problem. Another mistake is not properly defining the closed curve or surface in the integral. It is also important to pay attention to the direction and orientation of the curve or surface when applying the identity. Another mistake is not properly taking into account any boundary conditions or constraints. It is important to carefully follow the steps of the Vector Calculus Identity to avoid these and other common errors.