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anonymous

  • one year ago

1.) Find a ⋅ b. a = 7i - 4j, b = 4i + 3j <28, -12> 16 -40 <11, -1> 2.)Let u = <-4, 1>, v = <-1, 6>. Find -2u + 4v. <4, 22> <4, 7> <12, -26> <10, -14>

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  1. princeharryyy
    • one year ago
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    is that a-b

  2. anonymous
    • one year ago
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    @princeharryyy a times b

  3. princeharryyy
    • one year ago
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    the product @em2000

  4. anonymous
    • one year ago
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    yes

  5. princeharryyy
    • one year ago
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    multiply i by i and j by j

  6. anonymous
    • one year ago
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    i got <11, -1> for the final answer, is that what you got? @princeharryyy

  7. princeharryyy
    • one year ago
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    u added but we need to multiply

  8. princeharryyy
    • one year ago
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    try A

  9. princeharryyy
    • one year ago
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    what happened @em2000

  10. princeharryyy
    • one year ago
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    7*4 is 28 and -4*3 is -12

  11. anonymous
    • one year ago
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    @princeharryyy gotcha that makes sense. i got <12, -26> for #2 is that wrong?

  12. princeharryyy
    • one year ago
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    but before i tell you about the first and second answer, are you doing scalar vectors.

  13. princeharryyy
    • one year ago
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    @em2000

  14. anonymous
    • one year ago
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    @princeharryyy yes

  15. princeharryyy
    • one year ago
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    then it's my bad. the first ones answer won't be A part

  16. anonymous
    • one year ago
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    @princeharryyy actually im not sure, the instructions dont specify

  17. princeharryyy
    • one year ago
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    < and > means vectors that's why i asked

  18. princeharryyy
    • one year ago
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    let me tell how they work

  19. princeharryyy
    • one year ago
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    i.i =1, j.j =1 i.j =0 (iand j are at 90 degrees)

  20. princeharryyy
    • one year ago
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    |dw:1435096143456:dw|

  21. princeharryyy
    • one year ago
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    i, j, k are all at 90 degrees any two quantities when multiplied at 90 degrees gives 0 as i.j.cos90 =0, j.k.cos90 =0, k.i.cos90 =0

  22. princeharryyy
    • one year ago
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    are you getting it @em2000

  23. princeharryyy
    • one year ago
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    So, for the first question a = 7i - 4j, b = 4i + 3j a.b is written as a.b = (7i - 4j).(4i - 3j)

  24. princeharryyy
    • one year ago
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    so, a.b = 7*4*i.i -7*3*i.j -4*4*j.j-4*3j.j so, a.b = 28-0-0-12 =16 answer @em2000

  25. princeharryyy
    • one year ago
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    for the first question

  26. princeharryyy
    • one year ago
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    now for the second

  27. princeharryyy
    • one year ago
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    Let u = <-4, 1>, v = <-1, 6>. Find -2u + 4v. => u = -4i+1j, v = -1i+6j -2u+4v = -2(-4i+1j) +4(-1i+6j) = 8i-2j -4i+24j = 4i+22j => <4,22> answer @em2000

  28. princeharryyy
    • one year ago
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    which is option A @em2000 . Did you get it.

  29. mathstudent55
    • one year ago
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    Scalar multiplication of vectors: \(\bf{A} = \sf A_x + B_y\) \(\bf B = \sf B_x + B_y\) \(\bf A \cdot B \sf = A_xB_x + A_yB_y\) Answer is scalar.

  30. anonymous
    • one year ago
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    @princeharryyy thank u so much

  31. princeharryyy
    • one year ago
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    Do you know the answers now @em2000

  32. princeharryyy
    • one year ago
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    for first one it is 16 and for second one i t is <4,22> @em2000

  33. anonymous
    • one year ago
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    @princeharryyy yes

  34. princeharryyy
    • one year ago
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    :)

  35. mathstudent55
    • one year ago
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    \(\bf A \cdot B \sf = A_xB_x + A_yB_y = (7)(4) + (-4)(3) = 28 - 12 = 16\)

  36. mathstudent55
    • one year ago
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    |dw:1435096919904:dw|

  37. princeharryyy
    • one year ago
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    thanks @mathstudent55. Sorry, for the medal she patiently tried to understand the concept. That's why I gave her the medal. Sorry, that I can't offer them to two people on one question. @em2000 could you please give a medal to @mathstudent55

  38. princeharryyy
    • one year ago
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    @mathstudent55 tried to help you out as well.

  39. princeharryyy
    • one year ago
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    no not to me @em2000 , but to @mathstudent55

  40. mathstudent55
    • one year ago
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    @princeharryyy Don't worry about the medal. I gave you one because I thought your explanation was great, and you deserved it!

  41. princeharryyy
    • one year ago
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    I never worry about medals @mathstudent55 but most people at open study help others for medals.

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