Vector cross product identity proof

In summary: V and W to get the desired result. In summary, the problem can be solved by using the properties of the differential operator \nabla and the vector identity for the triple product.
  • #1
notReallyHere
3
0

Homework Statement




[tex] \bigtriangledown\times\\(v\times w)= v(\bigtriangledown\cdot w) - w(\bigtriangledown\cdot v)+ (v\cdot\bigtriangledown)w - (w\cdot\bigtriangledown) v [/tex]


I've tried expanding left side and get
[v1(dw2/dy+dw3/dz)-w1(dv2/dy+dv3/dz)]i +
[v2(dw3/dz+dw1/dx)-w2(dv3/dz+dv1/dx)]j +
[v3(dw1/dx+dw2/dy)-w3(dv2/dy+dv1/dx)]k

is this right way to start it? another way to attack it?
 
Physics news on Phys.org
  • #2
notReallyHere said:

Homework Statement




[tex] \bigtriangledown\times\\(v\times w)= v(\bigtriangledown\cdot w) - w(\bigtriangledown\cdot v)+ (v\cdot\bigtriangledown)w - (w\cdot\bigtriangledown) v [/tex]


I've tried expanding left side and get
[v1(dw2/dy+dw3/dz)-w1(dv2/dy+dv3/dz)]i +
[v2(dw3/dz+dw1/dx)-w2(dv3/dz+dv1/dx)]j +
[v3(dw1/dx+dw2/dy)-w3(dv2/dy+dv1/dx)]k

is this right way to start it? another way to attack it?

You can try the following: First note that [tex] \nabla [/tex] is a differential operator, so its action on the product is the sum of actions on each factor

[tex] \bigtriangledown\times\\(v\times w)= \bigtriangledown\times\\(V\times w) + \bigtriangledown\times\\(v\times W) [/tex]

(I used capital letters to denote the factor on which [tex] \nabla [/tex] acts in each term. The other factor can be treated as a constant). Then use the vector identity

[tex] a \times( b \times c) = b(a \cdot c) - c (a \cdot b) [/tex]
 

FAQ: Vector cross product identity proof

What is the vector cross product identity?

The vector cross product identity, also known as the triple vector product identity, is a mathematical equation that relates the cross product of three vectors to the dot product of those vectors. It states that the cross product of the cross product of two vectors is equal to the difference between the dot product of those vectors and the dot product of the first vector with the cross product of the second vector.

Why is the vector cross product identity important?

The vector cross product identity is important because it allows us to simplify complex vector equations and manipulate them in a more efficient manner. It is also a fundamental concept in vector calculus and is used in many areas of physics, engineering, and computer graphics.

How is the vector cross product identity derived?

The vector cross product identity can be derived using the properties of vector operations such as the distributive, commutative, and associative properties. It can also be derived using the geometric properties of the cross product and the properties of the dot product. The proof involves expanding both sides of the equation and simplifying them to show that they are equal.

Can the vector cross product identity be extended to higher dimensions?

Yes, the vector cross product identity can be extended to higher dimensions. In three-dimensional space, the cross product results in a vector, but in higher dimensions, it results in a higher-dimensional object such as a bivector or a trivector. The concept of the vector cross product identity can also be extended to these higher-dimensional objects.

What are some applications of the vector cross product identity?

The vector cross product identity has many applications, including in physics for calculating torque and angular momentum, in engineering for calculating moments of inertia and angular velocity, and in computer graphics for calculating the direction and intensity of light in 3D scenes. It is also used in vector calculus to solve problems involving vector fields and line integrals.

Back
Top