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Semi-major axis equation question

  1. Jul 4, 2013 #1
    1. The problem statement, all variables and given/known data

    Hi there, this isn't a homework question but I need some help with this equation since I'm not the best at mathematics. I would like to rearrange this equation so I can solve for "a"

    2. Relevant equations

    9k6xk0.gif

    3. The attempt at a solution

    ?
     
  2. jcsd
  3. Jul 4, 2013 #2

    Dick

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    Well, start by squaring both sides. That will get rid of the square root. How bad at mathematics are you?
     
  4. Jul 4, 2013 #3
    Im really bad at it!
     
  5. Jul 4, 2013 #4

    Dick

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    Good to know. What happens if you try squaring both sides? Do your worst.
     
  6. Jul 4, 2013 #5
    so you're saying

    f9nsit.gif
     
  7. Jul 4, 2013 #6

    Dick

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    That's pretty bad. You forgot to square the ##2 \pi##. And if you square a square root then you eliminate the square root. ##(\sqrt{x})^2=x##. Try and fix it up a little.
     
  8. Jul 4, 2013 #7
    Ok then, another attempt.

    2w4cwf8.gif
     
  9. Jul 4, 2013 #8

    Dick

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    Closer. Just write ##(2 \pi)^2## instead of ##2 \pi^2##. They mean different things don't they? I hope you know that much? The next step is to move everything except for ##a^3## to the left side of the equation. Know ANY algebra?
     
  10. Jul 4, 2013 #9
    Well considering I haven't taken a math course since high school which was about 8 years ago so I'm a little rusty as you can tell. But it's starting to come back to me somewhat. So should this be the final solution then?

    2lsblw4.jpg

    edit it should be (2pi)squared like u said
     
  11. Jul 4, 2013 #10

    Dick

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    Yes, that's right. Glad you got it if you write (2pi)^2. I didn't think you were going to make it for a while. Keep reviewing the algebra. It's not that hard and you need to know it.
     
  12. Jul 4, 2013 #11
    OK, thanks for you're help!
     
  13. Jul 4, 2013 #12

    Dick

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    You're welcome. Um, it's 'your help' not 'you're help' if you want to do grammar too. :)
     
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