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    I must differentiate:

    y = ((x^2)sin2x - 2x)(e^4x)cosx

    I've not done differentiation for a while, and need a bit of hinting what methods to use... in order would be nice too ;P

    All intended-to-help comments will be greatly appreciated=]
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    whoah no, actually they can be repped, how did i get from 1 to 5 green thingies over night?! =D
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    :lol: yeah, some users have rep power to turn you from red to green with a click. (and vice-versa!) :p:

    Before you start, just to confirm, do you mean this:

     y = ({x^2}sin^2{x} - 2x)(e^{4x}cosx)

    You need to use the product rule (with a bit of chain rule), multiple times:
     \dfrac{d}{dx}(u\cdot v)=u\cdot \dfrac{dv}{dx}+v\cdot \dfrac{du}{dx}

    (latex copied from wikipedia).

    i.e. make substitutions, make a={x^2}{sin^2}x and so \frac{da}{dx}= 2{x^2}sinxcosx+2x{sin^2}x
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    (Original post by jakash)
    :lol: yeah, some users have rep power to turn you from red to green with a click. (and vice-versa!) :p:

    Before you start, just to confirm, do you mean this:

     y = ({x^2}sin^2{x} - 2x)(e^{4x}cosx)
    hehe yeah I for once made a good, and noticeable comment :P

    and yes that's what i mean ^^
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    (Original post by jakash)
    :lol: yeah, some users have rep power to turn you from red to green with a click. (and vice-versa!) :p:

    Before you start, just to confirm, do you mean this:

     y = ({x^2}sin^2{x} - 2x)(e^{4x}cosx)

    You need to use the product rule, multiple times:
     \dfrac{d}{dx}(u\cdot v)=u\cdot \dfrac{dv}{dx}+v\cdot \dfrac{du}{dx}


    i.e. make substitutions, make
    (latex copied from wikipedia).
    no sorry , this is what i mean

     y = ({x^2}sin^2{x} - 3x)(e^{4x}cosx)

    3x, not 2x, but it wouldnt matter anyway, I just need to get the jist of which methods to use :]
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    that looks loooooooooong.
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    Do you need to use product rule not only within the brackets but between the brackets? Or can you just differentiate inside the brackets and keep them as separate brackets multiplying together?
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    Guys try this out
    http://www.numberempire.com/derivatives.php
    Its an online derivative calculator. Doesn't give you working but does give you the right answer.
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    (Original post by Formula 1)
    Guys try this out
    http://www.numberempire.com/derivatives.php
    Its an online derivative calculator. Doesn't give you working but does give you the right answer.
    It's all about the wolframalpha!
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    (Original post by Jukukiwaiyi)
    COMPLEX differentiation
    I see no "i"s here.

    :awesome:
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    (Original post by Small123)
    It's all about the wolframalpha!
    Yeah true wolfram is pretty decent. Forgot about that one. :p:
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    It will get very messy and will take a while, but if you keep it neat (use substitutions) and avoid mistakes by not taking too many short-cuts you'll get there soon.

    If you just want the answer

    EDIT: Grrr can't work the latex; its too complicated! :mad2:
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    I differentiated it, to get dy/dx = (x^2.sin^2x-2x)(-e^4x.sinx+4x^4x.cosx)+(e^4x.cosx )(x^2.cos^2x+2xsin^2x-2), then realised that it was -3x not -2x. . . FML haha.

    EDIT: it doesnt matter its wrong anyway =(, very messy question haha.
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    im ok with the differentiation bit, but my g0d the simplifying is messy!
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     \frac{dy}{dx} = e^{4x}\left(\cos x (2x \sin^2 x + x^2\sin2x - 3) + (4\cos x - \sin x)(x^2\sin^2x - 3x)\right)

    That's what I got by using the product rule a few times, dunno if it's right.
 
 
 
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