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How to solve an equation

  1. Mar 17, 2012 #1
    1. The problem statement, all variables and given/known data

    (V2-V1)^2 = 552+452-2*55*45*cos135

    = 92.5m/s



    My question is how to get from the first equation to the answer...
     
  2. jcsd
  3. Mar 17, 2012 #2
    552+452-2*55*45*cos135

    Is not solved correctly.
    It doesnt come up to 92.5(assuming the calculation you were working on didn't need change of units.
     
  4. Mar 17, 2012 #3
    its something from the course material, so i guess its just wrong....
     
  5. Mar 17, 2012 #4
    Yeah, it sounds like wrong.
    If you can perhaps add some back ground context we may be able to work out what the text wanted to convey :-)
     
  6. Mar 17, 2012 #5

    gneill

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    Staff: Mentor

    Looks suspiciously like an application of the cosine law where the exponents have lost their superscipt. Thus:

    ##x^2 = 55^2 + 45^2 - 2\cdot55\cdot45\cdot cos(135°) ##

    solve for x.
     
  7. Mar 17, 2012 #6
    haha! there we go thanks! i guess it it was just a typo in the course material.
     
  8. Mar 17, 2012 #7
    OMG!
    How did i miss that!
    That was incredible observation gneill
     
  9. Mar 17, 2012 #8

    gneill

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    Staff: Mentor

    I attribute it to to many hours doing math and not enough enjoying St. Patrick's day parties. I shall have to make amends :smile:
     
  10. Mar 17, 2012 #9
    I agree. Remarkable :smile:
     
  11. Mar 17, 2012 #10

    PeterO

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    Homework Helper

    What is supposed to be 92.5 m/s

    V2, V1 or the difference V2 - V1 ?
     
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