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Homework Help: Vector help asap

  1. Jan 12, 2005 #1
    vector help asap plz!!

    I have a problem that says define the i,j form of a vector and write the following vectors in i,j form u = P(1,1) to Q(2,4) and v = P(6, -3) to Q(7,0). I looked all through my book, and cannot find a definition for the i,j form of a vector ( i checked glossary, index,l and read the whole chapter again) I'm sure if i had a definition I could figure out how to re write the vectors...can anyone help please?
  2. jcsd
  3. Jan 12, 2005 #2


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    I don't know whether anyone can help,but hopefully i can.A vector in i+j form is expressed starting with its form in a basis.
    Exempli gratia:
    The vector [itex] \vec{A} [/itex] in the base [itex] \vec{i},\vec{j} [/itex]has the form:
    [tex] \vec{A}=5\vec{i}+7\vec{j} [/itex]
    ,so i step in and define its "i+j form" by the ordered pair:
    [tex] \vec{A}(\vec{i},\vec{j})=:(5,7) [/tex]

    Using this simple example,try to solve your problem.

    Last edited: Jan 12, 2005
  4. Jan 12, 2005 #3
    ok so for U for example, U in form i,j would be 1i + 1j and 2i + 4j ?? im lost a little or does this mean 2i + 1i = 3 and 4j + 1j = 5 so U(i,j) = (3,5) ??
  5. Jan 13, 2005 #4


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    Do you have no idea at all what a vector is?

    u is a vector from (1,1) to (2,4): The x component changes from 1 to 2 so it changes by 2-1= 1. The y component changes from 1 to 4 so it changes by 4-1= 3.
    The "i" number is the x change and the "j" number is the y change:
    u= 1i+ 3j (and that is NOT 4 anything!)

    v runs from (6, -3) to (7,0). The x component changes from 6 to 7: it changes by 1. The y component changes from -3 to 0: it changes by 0-(-3)= 3.
    v= 1i+ 3j (it's the same as u!)
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