Finding the Cross Product of A and B: A Puzzling Answer?

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Homework Help Overview

The discussion revolves around finding the cross product of two vectors A and B, specifically A = -3i + 4j and B = 2i + 3j. Participants are examining the calculations involved in determining the result of the cross product.

Discussion Character

  • Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are analyzing the calculation of the cross product, noting discrepancies in the results. One participant suggests that a negative sign may have been overlooked in the calculations, while another emphasizes the properties of the cross product, particularly the anticommutative nature of the operation.

Discussion Status

The discussion is ongoing, with participants providing insights and corrections regarding the calculation process. There is a focus on clarifying the steps involved in computing the cross product, but no consensus has been reached regarding the correct answer.

Contextual Notes

Participants are working within the constraints of the problem as posed, with specific attention to the definitions and properties of vector operations in the context of the cross product.

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Homework Statement



A = -3i + 4j and B = 2i + 3j

so I want to find AxB

Homework Equations





The Attempt at a Solution



what I got is -9k + 8k, which is -k but the answer solution says it's -17k ?
 
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You are missing a negative sign on the 8. Remember that when you take the cross product of two vectors, A and B, in the x-y plane you will get:

[tex](A_xB_y-A_yB_x)\hat{k}[/tex]

You are missing the minus sign in the above equation.
 
EDIT: This post refers to a post deleted by the OP.The i x i and j x j terms are zero by definition. You then have:

-9(i x j)+8(j x i)

Remember that the cross product anticommutes. So if ixj=k. What does this mean for j x i?
 
Last edited:
jxi is k?
 

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