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Math Help - Some sine equations

  1. #1
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    Some sine equations

    sin x=-0.9
    has solution x= 244.2
    what is the other solution?? HELP

    also

    cos y=-0.3
    y=107.5
    wot else?

    answers to 1dp
    Last edited by sasha9193; September 2nd 2007 at 11:16 AM.
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  2. #2
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    Remember that \sin(\pi-x)=\sin x and \cos(2\pi-x)=\cos x
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  3. #3
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    lol thats way beyond my league, can u give answers?
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by sasha9193 View Post
    sin x=-0.9
    has solution x= 244.2
    what is the other solution?? HELP

    also

    cos y=0.1
    y=84.3
    wot else?

    answers to 1dp
    Krizalid is correct. also, I should point out that there are infinitely many solutions since sine and cosine are periodic functions. you should state what interval you want them in

    usually questions ask for the solution in 0 \leq \theta \leq 2 \pi

    Krizalid's solution gives the solution in -2 \pi \leq \theta \leq 0 as it stands now. you may have to do a little tweeqing
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  5. #5
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    o yes sorry

    answers in 0<x<360
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  6. #6
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by sasha9193 View Post
    lol thats way beyond my league, can u give answers?
    x is the angle you are given. \pi = 180 degrees, 2 \pi = 360 degrees

    try it
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  7. #7
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    look above i just said the answers i need 0<x<360

    could u give me answers this is beyond me but i need the answer
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  8. #8
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by sasha9193 View Post
    look above i just said the answers i need 0<x<360

    could u give me answers this is beyond me but i need the answer
    the fact that users spit out answers sometimes makes people think that that's all we're here for. we don't like giving out answers if the user just mindlessly copies them down. if we see you make a valiant effort to understand we will help you. if you still don't get it, we will give you the answer and tell you to look over it carefully. please try to get it, it's for your own good. what specifically did you not understand from Krizalid's post?
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  9. #9
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    look i am at very low level of maths at the moment, the question is only just understandable to me im learning but this type of question at the moment is beyond me i just need the answer

    but i also understand your here to teach as well as just tell answers, but at the moment i am not up to the level you can start teaching me
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  10. #10
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by sasha9193 View Post
    look i am at very low level of maths at the moment, the question is only just understandable to me im learning but this type of question at the moment is beyond me i just need the answer

    but i also understand your here to teach as well as just tell answers, but at the moment i am not up to the level you can start teaching me
    the answer to the first is 295.8 degrees (the sine one)

    the answer to the second is 275.7 degrees (the cosine one)
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  11. #11
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    the second one has changed slightly plz check second one at top
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  12. #12
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by sasha9193 View Post
    the second one has changed slightly plz check second one at top
    the new answer is 252.5

    my final admonition: you will never get to the point where you can be taught and you can reason through something if you give up so easily. there is pretty much no one who gets up and understands everything without trying. you must work at it to get it. there are times when i spend hours, even days working on one problem, and i'm sure many of the other helpers here can testify to the same.
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