Did my book do this wrong? (Vector Cross Product)

Click For Summary
SUMMARY

The discussion confirms that the book contains errors in the calculation of the Vector Cross Product for the vectors (1, 3, -4) and (2, -5, 8). The correct calculation should yield the result (44, 0, -11), but the book incorrectly presents intermediate steps and final results. Specifically, the first row should be calculated as (3)(8) - (4)(-5) instead of (3)(8) - (-4)(-5), and the second row should be (4)(2) - (1)(8) instead of (-4)(2) - (1)(8). These misprints undermine the credibility of the author and the proofreading process.

PREREQUISITES
  • Understanding of vector mathematics
  • Familiarity with the Vector Cross Product
  • Basic algebraic manipulation skills
  • Knowledge of 3D coordinate systems
NEXT STEPS
  • Study the properties of the Vector Cross Product in 3D space
  • Learn about vector operations in linear algebra
  • Practice calculating cross products with various vector pairs
  • Review common errors in vector mathematics and how to avoid them
USEFUL FOR

Students of mathematics, educators teaching vector calculus, and anyone interested in 3D graphics or physics applications involving vector operations.

Pindrought
Messages
15
Reaction score
0
Reading a book about 3d math, and I am confused as to what happened on this Vector Cross Product problem. I'm thinking there was just an error that wasn't caught.

i92Cuh.png
For the first row, instead of (3)(8)-(-4)(-5) shouldn't it have been (3)(8)-(4)(-5) and had the same displayed result of 44?
And for the second row, instead of (-4)(2)-(1)(8) shouldn't it have been (4)(2)-(1)(8) and had the result of 0?
For the last row, shouldn't the final result be -11?

Thanks!
 
Last edited:
Physics news on Phys.org
The book is indeed wrong:

$(1,3,4) \times (2,-5,8) = ((3)(8) - (4)(-5), (4)(2) - (1)(8), (1)(-5) - (3)(2))$

$= (44,0,-11)$ which speaks somewhat ill of the original author and proof-reader of your text.
 
Pindrought said:
Reading a book about 3d math, and I am confused as to what happened on this Vector Cross Product problem. I'm thinking there was just an error that wasn't caught.

For the first row, instead of (3)(8)-(-4)(-5) shouldn't it have been (3)(8)-(4)(-5) and had the same displayed result of 4?
And for the second row, instead of (-4)(2)-(1)(8) shouldn't it have been (4)(2)-(1)(8) and had the result of 0?
For the last row, shouldn't the final result be -11?

Thanks!
There are at least two misprints/errors in the example. It looks as though the author intended to write $$\begin{bmatrix}1\\3\\ {\color{red}-}4 \end{bmatrix} \times \begin{bmatrix}2\\-5\\ 8 \end{bmatrix} = \begin{bmatrix}(3)(8) - (-4)(-5)\\(-4)(2) - (1)(8)\\ (1)(-5) - (3)(2) \end{bmatrix} = \begin{bmatrix}4\\-16\\ {\color{red}-11} \end{bmatrix}.$$
 
Thank you very much!
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
Replies
5
Views
5K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
1K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 7 ·
Replies
7
Views
1K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K