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Vector cross product

  • Thread starter Ry122
  • Start date
  • #1
565
2
What is the cross product of -i x i? Is it negative 1 or is still just 0?
 

Answers and Replies

  • #2
Defennder
Homework Helper
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Note that for any 2 vectors a,b: -a x b = -(a x b). This reduces the problem to -(i x i).

Now what is the vector product of a vector with itself?
 
  • #3
565
2
well can you tell me how the projection of u on to v
where
u=-i+2j and v=i+2j is
v=(3/5)i+(6/5)j ?
The answer i got was (4/5)i + (8/5)j
i used the equation
w=v.((u.v)/(modulusv^2))
 
  • #4
D H
Staff Emeritus
Science Advisor
Insights Author
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i used the equation
w=v.((u.v)/(modulusv^2))
This equation for the projection is

[tex]\mathbf w = \mathbf v \frac {\mathbf u \cdot \mathbf v}{v^2}[/tex]

Note well: The cross product is not involved when you compute the projection this way.
 
  • #5
565
2
That's the same equation that I gave. yeah i realized my mistake after posting, i should have said dot product, not cross product.
 

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