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Math Help - Me again, dunno wot I am gonna do wif maths! lol

  1. #1
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    Me again, dunno wot I am gonna do wif maths! lol

    cos2B+cosB
    sin2B-sinB
    =
    cosb+1
    sinB

    start on TOP
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  2. #2
    Moo
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    Hello,

    Let's see the denominator :
    \sin(2b)=2\cos(b)\sin(b)

    Hence \sin(2b)-\sin(b)=\sin(b)(2 \cos(b)-1)

    Do you see the thing ? Do you see which formula for cos(2b) you will have to use ?

    \cos(2b)=2 \cos^2(b)-1

    So \cos(2b)+\cos(b)=2 \cos^2(b)-1+\cos(b)

    Now this is the tricky thing :

    =2 \cos^2(b)+2 \cos(b)-\cos(b)-1=2 \cos(b)(\cos(b)+1)-(\cos(b)+1) =(\cos(b)+1)(2 \cos(b)-1)

    How did I know it ? Because I know where I want to go

    --------> \frac{\cos(2b)+\cos(b)}{\sin(2b)-\sin(b)}=\frac{(\cos(b)+1){\color{red} (2 \cos(b)-1)}}{\sin(b) {\color{red} (2 \cos(b)-1)}}

    =\frac{\cos(b)+1}{\sin(b)}
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  3. #3
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    Seeing that I thanked you for your hard work, please help with this one


    http://www.mathhelpforum.com/math-he...h-problem.html
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