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    who can do these?

    1. e^xsec^2(e^x) dx
    2. 1/xlnx dx
    3. 2x/x^4+1 dx

    MORE TO COME FOR ALL YOU KEEN BEANS!!!
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    1) tan(e^x) + C
    2) 1/2(lnx)^2 + C
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    1,3
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    (Original post by Ralfskini)
    1) tan(e^x) + C
    2) 1/2(lnx)^2 + C
    howd you do 2
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    (Original post by kikzen)
    howd you do 2
    i think ralfskini interpreted the qu. as (1/x).lnx dx
    so integrating this would just be a matter of spotting that the differential of (lnx) is (1/x), so you get (1/2)(lnx)^2 +c

    I thought the question was like this though: INT 1/(xlnx) dx
    For this, I would use the substitution, u=lnx.....and I got ln(lnx) + C as the answer
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    Question 2 is easy peazzzzzy

    Intergrate (1/x)lnx

    define u= lnx v'= (1/x)
    u'=(1/x) v= lnx

    {(1/x)lnx.dx = (lnx)^2 - {(1/x)lnx.dx

    Simplify by bringin identical integrals together:

    2{(1/x)lnx.dx= (lnx)^2

    And the answer is
    {(1/x)lnx.dx= [(lnx)^2]/2
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    By the way { is my integral symbol
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    (Original post by mathsgeek)
    Question 2 is easy peazzzzzy

    Intergrate (1/x)lnx

    define u= lnx v'= (1/x)
    u'=(1/x) v= lnx

    {(1/x)lnx.dx = (lnx)^2 - {(1/x)lnx.dx

    Simplify by bringin identical integrals together:

    2{(1/x)lnx.dx= (lnx)^2

    And the answer is
    {(1/x)lnx.dx= [(lnx)^2]/2
    what the?

    i tot the question was

    1/(xlnx)
    you answered
    ln x / x
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    1/xlnx is the same as (1/x)*lnx which is waht i answered dumb arse, lol
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    argh...thats darn weird ya know..
    cant seem to understand your working though..
    anyways..maybe its the typo which confuses me
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    sorry malasian dude ur right, im the dumb arse
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    (Original post by mathsgeek)
    sorry malasian dude ur right, im the dumb arse
    no no, it just depends how you read the question,

    I mean 1/xlnx dx would appear to mean 1/(xlnx) but according BIDMAS (or whatever you call it) you do division first, so it would be (1/x)*(lnx) - so it just depends on the brackets - so inwhich case you were right
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    (Original post by kikzen)
    1,3
    Heh, how'd you know about 1/(1 + x^2) being d/dx (arctan x)? If it's Edexcel P3, they wouldn't want that.. wouldn't they want partial fractions or something instead?
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    (Original post by Nylex)
    Heh, how'd you know about 1/(1 + x^2) being d/dx (arctan x)? If it's Edexcel P3, they wouldn't want that.. wouldn't they want partial fractions or something instead?
    Note to the first poster:- whereabouts should the brackets be for question 2?
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    1/(xlnx)
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    (Original post by BigJohn)
    1/(xlnx)
    was my answer right then.....ln(lnx) + C ???
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    It's nice that you guys know the answers, but it would be greta if you could show your working.
    I can do most of the Q's in the P3 book but my new tutor (my maths crazy uncle) set me these crazy questions and I can't remember anything since our last lesson.
    Next
    (x+1)^2e^x
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    I got 1/(2xlnx)
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    (Original post by BigJohn)
    It's nice that you guys know the answers, but it would be greta if you could show your working.
    I can do most of the Q's in the P3 book but my new tutor (my maths crazy uncle) set me these crazy questions and I can't remember anything since our last lesson.
    Next
    (x+1)^2e^x
    Which answer is right?!
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    Actually I just get 1/2
 
 
 

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