Quaternion Multiplication: Expanding and Simplifying

In summary, the product of two quaternions can be expanded and simplified by multiplying each term with every other term and rearranging the resulting ijk terms according to their non-commutative multiplication rules. This is justified by the fact that quaternion multiplication distributes over addition, as defined.
  • #1
flash
68
0

Homework Statement


Expand and simplify the product of two quaternions:

(3 + 2i + 3j + 4k)(3 + 3i + 2j + 5k)

Justify your response.


The Attempt at a Solution



I have done this by expanding brackets normally, keeping the ijk's in the same order because the multiplication is not commutative. I have the correct answer, I just can't think how to justify it. Why should expanding brackets necessarily work?
 
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  • #2
flash said:
Why should expanding brackets necessarily work?

Isn't that how multiplication of the quaternions is defined?
 
Last edited:
  • #3
flash said:
Why should expanding brackets necessarily work?

It works necessarily because quaternion multiplication distributes over quaternion addition per the definitions of quaternion multiplication and addition.
 
  • #4
Thanks guys, that's all I needed.:cool:
 

Related to Quaternion Multiplication: Expanding and Simplifying

1. What are quaternions?

Quaternions are a four-dimensional extension of complex numbers that are used to represent rotations and orientations in three-dimensional space.

2. How do you multiply quaternions?

To multiply quaternions, you use the formula (a + bi + cj + dk)(x + yi + zj + wk) = (ax - by - cz - dw) + (aw + bx + cy - dz)i + (az - bw + cx + dy)j + (ay + bz + cw + dx)k. Essentially, you distribute and combine like terms as you would with regular algebraic multiplication.

3. What is the significance of quaternion multiplication?

Quaternion multiplication is significant because it allows for easy and efficient representation of 3D rotations and orientations. It is also useful in fields such as computer graphics, robotics, and physics.

4. How is quaternion multiplication different from regular multiplication?

Quaternion multiplication differs from regular multiplication in that it is non-commutative, meaning that the order in which the quaternions are multiplied matters. It is also non-associative, meaning that the grouping of the quaternions can affect the result.

5. Can quaternions be divided?

Technically, quaternions can be divided, but it is not a common operation and is not as straightforward as multiplication. Division of quaternions is also not commutative or associative, and the result may not always be a valid quaternion.

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