Does the following cross product identity always work?

In summary, the conversation discusses the standard basis vectors and the vector triple product identity. It is mentioned that the identity only works for orthogonal vectors, such as the standard basis vectors, but not for all vectors. The example of A=0 is given to demonstrate this.
  • #1
em370
24
1
Mod note: Reproduced contents of image with broken link:
i = j x k
j = k x i
k = i x j

Wikipedia says this about the standard basis vectors. Does this work for all (i.e, non basis) vectors? For example, if you know A = B X C does that mean C = A X B and B = C X A?
 
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  • #2
Nope. Let's start with ##A = B \times C## and see what ##A \times B## gives us. Using the vector triple product identity, we have ##A \times B = (B\times C) \times B = C (B\cdot B) - B (B \cdot C)##. So, ##A \times B = C## only if ##B## and ##C## are orthogonal (i.e. their dot product is zero) - which is true for the standard basis vectors, but not true in general.
 
  • #3
Have you tried ##A=0##?
 

Related to Does the following cross product identity always work?

1. What is a cross product identity?

A cross product identity is a mathematical equation that relates the cross product of two vectors to the dot product of those vectors and their magnitudes. It is often used in vector calculus and is an important concept in physics and engineering.

2. How is the cross product identity used?

The cross product identity is used to simplify complex vector equations and to find relationships between different vector quantities. It is also used to calculate the cross product of two vectors when only the dot product is known.

3. Does the cross product identity always work?

Yes, the cross product identity always works as it is a fundamental mathematical concept that is based on the properties of cross and dot products. It is applicable to all types of vectors and can be used in any vector operation.

4. What are the benefits of using the cross product identity?

Using the cross product identity can help simplify and solve complex vector equations, especially in physics and engineering applications. It also allows for the calculation of the cross product using only the dot product, which can save time and effort in certain situations.

5. Are there any limitations to the cross product identity?

The cross product identity is limited to 3-dimensional vectors and cannot be applied to higher dimensions. Additionally, it can only be used with orthogonal vectors, meaning that the angle between them must be 90 degrees.

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