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    sin(x + π) = -sin(x) ?

    Someone tell me how this is?
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    Can someone help me with this question

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    its from june 2009
    Having trouble with part ii
    thx

    xxx
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    (Original post by Hody421)
    sin(x + π) = -sin(x) ?

    Someone tell me how this is?
    Just consider the period of the sin graph.
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    (Original post by emi1996)
    Can someone help me with this question

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    its from june 2009
    Having trouble with part ii
    thx

    xxx
    Replace the second bracketed term in part A with the result found part B.
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    (Original post by Hody421)
    sin(x + π) = -sin(x) ?

    Someone tell me how this is?
    there you go!
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    (Original post by emi1996)
    Can someone help me with this question

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    its from june 2009
    Having trouble with part ii
    thx

    xxx
    If x > y then x – y > 0
    (x + 0.5y)^2+ (3/4)y^2is greater than 0 since it is the sum oftwo squares
    so x^2+ xy + y^2 > 0
    Therefore (x – y)(x^2+ xy + y^2) > 0

    So x^3– y^3> 0
    i.e. x^3> y^3
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    Ive been put in for the core 3 exam early and have no clue what im doing frustrated cuz ill definately need to retake next year
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    (Original post by lizard54142)
    Just consider the period of the sin graph.
    what is the period of a sin, cos and tan graph?
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    http://www.thestudentroom.co.uk/atta...hmentid=425525

    Anyone know what exam paper that is from?
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    (Original post by messupp)
    If x > y then x – y > 0
    (x + 0.5y)^2+ (3/4)y^2is greater than 0 since it is the sum oftwo squares
    so x^2+ xy + y^2 > 0
    Therefore (x – y)(x^2+ xy + y^2) > 0

    So x^3– y^3> 0
    i.e. x^3> y^3
    Thx!
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    How do you know when to use integration by substitution? Is there a rule or do you just use it when you don't think any other method would work?

    e.g. how would you know to use substitution for this: (or is there another method that works for this Q?) Name:  Picture1.png
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    (Original post by [email protected])
    what is the period of a sin, cos and tan graph?
    tan\theta = tan(\theta \pm n\pi)

    cos\theta = cos(\theta \pm 2n\pi)

    sin\theta = sin(\theta \pm 2n\pi)
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    Jan 2012
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    (Original post by tingirl)
    How do you know when to use integration by substitution? Is there a rule or do you just use it when you don't think any other method would work?

    e.g. how would you know to use substitution for this: (or is there another method that works for this Q?) Name:  Picture1.png
Views: 230
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    You can actually integrate this directly (because it is a linear function in the square root), so you don't need to use a substitution if you don't want to. Rewrite it as (3x-2)^{-1/2}
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    (Original post by lizard54142)
    tan\theta = tan(\theta \pm n\pi)

    cos\theta = cos(\theta \pm 2n\pi)

    sin\theta = sin(\theta \pm 2n\pi)
    There was a question that wanted you to state an actually answer like 180 degrees??
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    (Original post by [email protected])
    There was a question that wanted you to state an actually answer like 180 degrees??
    Yeah, I just told you the periods!

    Tangent has a period of \pi or 180 degrees, Sine and Cosine both have a period of 2\pi or 360 degrees.
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    (Original post by lizard54142)
    You can actually integrate this directly (because it is a linear function in the square root), so you don't need to use a substitution if you don't want to. Rewrite it as (3x-2)^{-1/2}
    OH YEAH!!! Thanks! I think I get it now - if there was a fraction with x^2 in the denominator and no x in the numerator, you'd use substitution, right?
    I hope they just tell us when to use substitution
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    (Original post by tingirl)
    OH YEAH!!! Thanks! I think I get it now - if there was a fraction with x^2 in the denominator and no x in the numerator, you'd use substitution, right?
    I hope they just tell us when to use substitution
    From doing past papers they do seem to tell you if you need to do a substitution but this doesn't mean they always will! If the function being integrated looks like something you might use the chain rule on to differentiate, you might want to consider a substitution.
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    (Original post by Hody421)
    sin(x + π) = -sin(x) ?

    Someone tell me how this is?
    Its a sin graph shifted 180 degrees to the left, so its a negative sign graph. Try drawing it or visualizing it being shifted to the left
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    Good luck everyone. This should be our easiest exam so let's smash it....


    ...then worry about C4 later ;D
 
 
 
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