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anonymous

  • one year ago

Medal award! Suppose you start at the point (1,0) on a unit circle and move a distance t = 4.5 along the circle. What is the reference number for t? Give an exact answer. Your answer may have pi in it! Please PREVIEW! The reference number for 4.5 is t⎯

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  1. anonymous
    • one year ago
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    i have no idea what a "reference number" is , do you know?

  2. anonymous
    • one year ago
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    i have a guess, my guess is \(2\pi-4.5\) but that is really just a guess

  3. anonymous
    • one year ago
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    it's the same as a reference angle

  4. anonymous
    • one year ago
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    oh, that kind of begs the question is a "reference angle" between \(0\) and\(\frac{\pi}{2}\)?

  5. anonymous
    • one year ago
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    I believe so

  6. zepdrix
    • one year ago
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    Hmm ya the wording is a little strange here :d So we're starting at pi/2, ya? We're spinning 4.5 around,\[\large\rm \frac{\pi}{2}+4.5\]The way we get back to the reference angle depends on which quadrant we lie in. Turns out we're in quadrant 4, so to get our reference angle we would do \(\large\rm 2\pi-\theta\) So I guess we haveeeeee\[\large\rm 2\pi-\left(\frac{\pi}{2}+4.5\right)\]That seems kinda complicated though >.< Maybe that's not what they wanted hmm

  7. anonymous
    • one year ago
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    zepdrix no I put that in it was incorrect :/

  8. zepdrix
    • one year ago
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    Oh I'm so silly. We're starting at (1,0), not at (0,1)... So we're starting at an angle of 0, not pi/2.

  9. zepdrix
    • one year ago
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    Spinning to 4.5 puts us at \(\large\rm 0+4.5\) which is in quadrant 3. So to get back to our reference angle we would do \(\large\rm 4.5-\pi\).

  10. anonymous
    • one year ago
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    thanks so much :) may I ask how you got 4.5?

  11. zepdrix
    • one year ago
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    |dw:1444007447856:dw|Here is a handy chart showing you how to get your reference angle from each quadrant.

  12. zepdrix
    • one year ago
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    |dw:1444007656117:dw|So we started here at (1,0).

  13. zepdrix
    • one year ago
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    |dw:1444007714494:dw|If we pi radians around the circle, we'd be going approximately 3.14 around.

  14. zepdrix
    • one year ago
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    |dw:1444007764708:dw|But they told us to go 4.5 around. So we have to go further. To figure out which quadrant you should be in, you need the decimal value for 3pi/2.

  15. zepdrix
    • one year ago
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    3pi/2 ends up being approximately 4.7 4.5 is smaller than that value, so we're in quadrant 3! :)

  16. zepdrix
    • one year ago
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    And if you look back at my original chart, it shows you how to get from quad 3 to reference angle.

  17. anonymous
    • one year ago
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    ok :) thanks so much.. it's actually 3.5 not 4.5 though

  18. zepdrix
    • one year ago
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    what? 0_o it says 4.5 twice in the problem though lol

  19. anonymous
    • one year ago
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    I have one that I was working on that's exactly the same for practice :) Thanks so much

  20. zepdrix
    • one year ago
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    oh cool :3

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