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Thread: HSC 2018-2019 MX2 Integration Marathon

  1. #76
    -insert title here- Paradoxica's Avatar
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    Re: HSC 2018 MX2 Integration Marathon

    Quote Originally Posted by stupid_girl View Post
    This is a skeleton solution.
    By substituting u=(x-2)/sqrt(2) and considering f(x)+f(-x), the integral can be re-written as


    A tangent substitution will turn it into a format that Wolfram can solve...finally

    https://www.wolframalpha.com/input/?...+(1-tan%5E2+x)

    I know Wolfram used hyperbolic tangent substitution but it is also solvable in MX2 by secant substitution.

    Alternatively, if you don't mind handling improper integral, you can do some algebraic manipulation to get:

    Substituting v=u-1+u and w=u-1-u will lead to two improper (but solvable) integrals because u-1 blows up at 0.
    *soluble
    If I am a conic section, then my e = ∞

    Just so we don't have this discussion in the future, my definition of the natural numbers includes 0.

  2. #77
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    Re: HSC 2018 MX2 Integration Marathon

    Quote Originally Posted by HeroWise View Post
    I think this is my first "Stupid_girl's Integrals" ill get. Maybe idk



    Well didnt get a but got a Thats outta be good right?

    I had to graph the thing, is it possible without graphing it?
    That's correct, but you don't need to graph the function, you just need to know the sign of the thing under the absolutes at every point in the region.
    If I am a conic section, then my e = ∞

    Just so we don't have this discussion in the future, my definition of the natural numbers includes 0.

  3. #78
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    Re: HSC 2018 MX2 Integration Marathon

    The next task is to find the indefinite integral. Of course the answer is not sin x-cos x+c.


    Hint: You may consider the floor function.

  4. #79
    Junior Member HeroWise's Avatar
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    Re: HSC 2018 MX2 Integration Marathon

    damn floor function in extension 2 nani?!??!

    I mean, ill see ways to do it. Thanks for these beautidul integration qtns

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    Re: HSC 2018 MX2 Integration Marathon

    Quote Originally Posted by HeroWise View Post
    damn floor function in extension 2 nani?!??!

    I mean, ill see ways to do it. Thanks for these beautidul integration qtns
    1989 last question?

  6. #81
    Junior Member HeroWise's Avatar
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    Re: HSC 2018 MX2 Integration Marathon

    Oooooof fam thats old old old syllabus. They had arc length and HS in those days.

    Btw im sitting it next year, So do u recommend visiting these topics?

  7. #82
    -insert title here- Paradoxica's Avatar
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    Re: HSC 2018 MX2 Integration Marathon

    Quote Originally Posted by stupid_girl View Post
    The next task is to find the indefinite integral. Of course the answer is not sin x-cos x+c.


    Hint: You may consider the floor function.
    There is a mathematical algorithms paper exploring the construction of an algorithm that can find the continuous primitive of these example periodic functions which are typically done using substitutions that result in countable discontinuities.
    If I am a conic section, then my e = ∞

    Just so we don't have this discussion in the future, my definition of the natural numbers includes 0.

  8. #83
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    Re: HSC 2018 MX2 Integration Marathon

    This one requires the same trick you've seen.

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    Re: HSC 2018 MX2 Integration Marathon

    Quote Originally Posted by stupid_girl View Post
    The next task is to find the indefinite integral. Of course the answer is not sin x-cos x+c.


    Hint: You may consider the floor function.
    This is one possible answer.


    By exploiting the periodicity of tan-1(tan x), it can also be expressed as
    Last edited by stupid_girl; 9 Feb 2019 at 7:10 PM.

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    Re: HSC 2018 MX2 Integration Marathon

    Quote Originally Posted by stupid_girl View Post
    This one is absolutely a beast.
    This is quite similar to the other beast.






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    Re: HSC 2018 MX2 Integration Marathon

    Quote Originally Posted by stupid_girl View Post
    This is a skeleton solution.
    By substituting u=(x-2)/sqrt(2) and considering f(x)+f(-x), the integral can be re-written as


    A tangent substitution will turn it into a format that Wolfram can solve...finally

    https://www.wolframalpha.com/input/?...+(1-tan%5E2+x)

    I know Wolfram used hyperbolic tangent substitution but it is also solvable in MX2 by secant substitution.

    Alternatively, if you don't mind handling improper integral, you can do some algebraic manipulation to get:

    Substituting v=u-1+u and w=u-1-u will lead to two improper (but solvable) integrals because u-1 blows up at 0.
    Not sure if anyone attempted to go further from this.

    If you are careful with the manipulation, you should have got the final answer.










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    Re: HSC 2018 MX2 Integration Marathon

    I saw another approach on the internet...however the back substitution may be slightly messier.

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    Re: HSC 2018 MX2 Integration Marathon

    This is slightly tedious.
    Last edited by stupid_girl; 15 Feb 2019 at 12:10 PM.

  14. #89
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    Re: HSC 2018 MX2 Integration Marathon

    Quote Originally Posted by stupid_girl View Post
    I saw another approach on the internet...however the back substitution may be slightly messier.
    This only works for x>0 because the resultant primitive does not have a derivative at 0, yet the function to be integrated is clearly defined at 0.
    If I am a conic section, then my e = ∞

    Just so we don't have this discussion in the future, my definition of the natural numbers includes 0.

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    Re: HSC 2018-2019 MX2 Integration Marathon

    #83 and #88 are still outstanding and this is a new one.
    Feel free to share your attempt.

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