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Math Help - *Trigonometry Equations*

  1. #1
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    *Trigonometry Equations*

    Hey guys!

    Could you explain how to resolve, step by step, the following equations(or at least lines d) and e) )




    Thanks in advance!
    Attached Thumbnails Attached Thumbnails *Trigonometry Equations*-img_20111022_210239.jpg  
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  2. #2
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    Re: *Trigonometry Equations*

    Show us some work.

    What do you have?

    Where are you stuck?
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  3. #3
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    Re: *Trigonometry Equations*

    Quote Originally Posted by SammyS View Post
    Show us some work.

    What do you have?

    Where are you stuck?
    sen(x+x/4) = -1/2

    5x/4 = -π/6 + 2πK V 7π/6 +2πk, KeZ

    x= -4π/30 + 8/5πk V 28π/30 + 8/5πk, keZ

    x= -2/15π +8/5π V 14/15π + 8/5πk, keZ



    e)
    senxcosx = senx/2
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  4. #4
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    Re: *Trigonometry Equations*

    Quote Originally Posted by JohnTerry View Post

    e)
    senxcosx = senx/2
    Assuming sen(x) = sin(x)

    It is better to factorise so you do not inadvertently divide by 0 or discard solutions.

    \sin(x)- 2 \sin(x)\cos(x) =0 \Leftrightarrow \sin(x)(2-\cos(x))=0
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  5. #5
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    Re: *Trigonometry Equations*

    Quote Originally Posted by e^(i*pi) View Post
    Assuming sen(x) = sin(x)

    It is better to factorise so you do not inadvertently divide by 0 or discard solutions.

    \sin(x)- 2 \sin(x)\cos(x) =0 \Leftrightarrow \sin(x)(2-\cos(x))=0
    But where did the first sin(x) go?

    It is possible to solve the equation if you factorise it, but then we assume that the first sin(x)=0? Then, sin(x)=0; sin(x)=0 ; cos(x)=2

    And can you please confirm the first equation(d). The answer in the book is different.


    Thanks in advance!
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  6. #6
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    Re: *Trigonometry Equations*

    Quote Originally Posted by JohnTerry View Post
    Hey guys!

    Could you explain how to resolve, step by step, the following equations(or at least lines d) and e) )




    Thanks in advance!
    Please don't post more than two questions in a thread. Otherwise the thread can get convoluted and difficult to follow. See rule #8: http://www.mathhelpforum.com/math-he...hp?do=vsarules.

    Thread closed. Please post according to the rules, and please type the questions.
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