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Help with vectors.

  • Thread starter sibiryk
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  • #1
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First I want to say hello to everyone in here. I'm a noob.

Here is my problem.
Let u=(1.2.0), v=(0,0,3), and w=(0,1,0) are vectors in R^3.
Evaluate, if defined, the following expretions (if undefined state so)

a) (u * v)w
b) u+w*v
c) (u * u)/w
d) (v * v)/(w * w)


Should I try to calculate them or just tell if expretion is defined or undefined?
How can I tell if expretions above are defined?
 

Answers and Replies

  • #2
James R
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Should I try to calculate them or just tell if expretion is defined or undefined?
Read the instructions in the question!

Is "*" supposed to represent a dot product, or cross product?
 
  • #3
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James R said:
Read the instructions in the question!

Is "*" supposed to represent a dot product, or cross product?
It is a dot product.
 
  • #4
EnumaElish
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"Evaluate" means "calculate."

If you calculate and get a definite answer (a real number or vector) then it is defined.
 
  • #5
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Are my answers correct?

a) 0
b) undefined ( I don't see how I can add scalar to vector)
c) undefined
d) 9
 
  • #6
HallsofIvy
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a, b, c are correct (you are correct that you can't add a scalar to a vector. In c, division by a vector is not defined). However, in
d) (v * v)/(w * w)
The answer is clearly a fraction.
 
  • #7
James R
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The answer to (d) is correct. It's 9.
 
  • #8
HallsofIvy
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Hey, 9/1 is a fraction!! (blushing)
 

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