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Homework Help: Harmonic Motion in One dimension -- Question in equation derivation

  1. Mar 12, 2015 #1
    1. The problem statement, all variables and given/known data
    I am curious as to how the second line in the equation is equal to the third line in the equation. The book my class is using is Taylor and it just skips so many steps. What happens to the sign, I know this must relate to euler in some way I am just not sure how. Thank you
    I am just curious as to why and how

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 12, 2015 #2


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    Hello Futurestar33. Welcome to PF !

    Use angle addition/subtraction formula on cos(ωt - δ) .
  4. Mar 12, 2015 #3


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  5. Mar 12, 2015 #4


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    I don't see why they include the second line, seems irrelevant since cos(theta) = cos(-theta)
  6. Mar 12, 2015 #5
    Thank you guys
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