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Math Help - Trigonometric solution of cos x =.37

  1. #1
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    Trigonometric solution of cos x =.37

    I don't understand what to do. It says use a calculator when necessary.
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  2. #2
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    are you from GDUB?
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  3. #3
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    no whats that? the answer of the problem is:

    plus or minus 1.1918 + 2npi

    then n = 0, plus or minus 1, plus or minus 2.....
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  4. #4
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    Hey, what I meant by GDUB is Glenbard West High School. Are you from that school? Cause the question you posted is the exact same one I'm working on. Do you have a green precalculus book?
    Lol, i just thought it was so weird
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  5. #5
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    is there like a waterdrop on the book? if so thats mine lol. I have no idea how to solve this.
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  6. #6
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    lol, no water drop. the book is mostly green. the seventh edition one. sorry i'm not much help either. i just got on this chapter too. i posted something right before you, should check it out and see if its similar questions to your book.
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  7. #7
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    alright thanks. Mine is the 6th edition haha. You're an edition ahead of me.
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  8. #8
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    First, make sure your calculator is in "radian" mode, not degrees. Your calculator has an "inverse" button and a "cosine" button. Press "inverse", "cosine", then enter the number and "return". That will give you the "principal value, between -\pi and \pi.

    Because cosine is an "even function", cos(x)= cos(-x), the negative of that value is a solution also- that's why they say "plus or minus". And cosine is periodic with period 2\pi. That's why adding " 2n\pi" for any integer n also is an answer.
    Last edited by HallsofIvy; February 11th 2010 at 04:40 AM.
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