Page 5 of 6 FirstFirst ... 3456 LastLast
Results 101 to 125 of 130

Thread: Cool problem of the day!

  1. #101
    Executive Member asianese's Avatar
    Join Date
    Sep 2010
    HSC
    2012
    Gender
    Male
    Posts
    1,397
    Rep Power
    2

    Re: Cool problem of the day!

    I'm assuming that means sit snugly inside the parabola? OMG I JUST SOLVED IT!! SO HAPPY WTF OMG HAHHAHAHAHA. I feel...so smart...yet among some of these questions...

    The general equation of a circle is . Here . Solving simultaneously the parabola and circle, . As the solution is a double root, the discriminant equals 0. . . The circle has centre .

    By a similar process, the centre of the circle in the parabola is (Different k to top one)
    Last edited by asianese; 28 May 2012 at 11:58 PM.
    USYD: B Sc (Adv Maths) / (B A)? I

  2. #102
    Moderator Carrotsticks's Avatar
    Join Date
    Jun 2009
    HSC
    N/A
    Gender
    Undisclosed
    Posts
    6,201
    Rep Power
    7

    Re: Cool problem of the day!

    Quote Originally Posted by asianese View Post
    I'm assuming that means sit snugly inside the parabola?
    More snuggled up than me on a cold Sunday morning under my warm blanket.
    Bachelor of Science (Adv. Mathematics) - University of Sydney:

  3. #103
    Senior Member qwerty44's Avatar
    Join Date
    Oct 2011
    HSC
    2013
    Gender
    Male
    Posts
    561
    Rep Power
    2

    Re: Cool problem of the day!

    This thread is practically dead, so thought I might post a question. But unlike many of the others posted so far, a 2U student can do it.


  4. #104
    Junior Member ismeta's Avatar
    Join Date
    Feb 2012
    HSC
    2012
    Gender
    Female
    Posts
    186
    Rep Power
    1

    Re: Cool problem of the day!

    1? I didn't use any particular mathematical method to do it, though.
    "It was my husband's, before he died." "Oh...I'm sorry." "Don't be, I killed him."
    University of New South Wales - Computer Science

  5. #105
    Senior Member qwerty44's Avatar
    Join Date
    Oct 2011
    HSC
    2013
    Gender
    Male
    Posts
    561
    Rep Power
    2

    Re: Cool problem of the day!

    Quote Originally Posted by ismeta View Post
    1? I didn't use any particular mathematical method to do it, though.
    haha yeh, but you have to show how to get the answer.

    I guessed that the first time aswell :P

  6. #106
    ಠ_ಠ Sy123's Avatar
    Join Date
    Nov 2011
    HSC
    2013
    Gender
    Male
    Posts
    1,761
    Rep Power
    3

    Re: Cool problem of the day!

    Quote Originally Posted by qwerty44 View Post
    This thread is practically dead, so thought I might post a question. But unlike many of the others posted so far, a 2U student can do it.





    I think the conclusion is that a can indeed equal to b, but you gave us restricted boundaries, so yeah heh.
    'An art, which has an aim to achieve the beauty, is called a philosophy or in the absolute sense it is named wisdom.'- Al Farabi

  7. #107
    Senior Member qwerty44's Avatar
    Join Date
    Oct 2011
    HSC
    2013
    Gender
    Male
    Posts
    561
    Rep Power
    2

    Re: Cool problem of the day!

    Quote Originally Posted by Sy123 View Post




    I think the conclusion is that a can indeed equal to b, but you gave us restricted boundaries, so yeah heh.


    ^I tried to do it without log laws, so that's how I did it.

  8. #108
    Senior Member qwerty44's Avatar
    Join Date
    Oct 2011
    HSC
    2013
    Gender
    Male
    Posts
    561
    Rep Power
    2

    Re: Cool problem of the day!



    The curves are arcs of circles whose centers are vertices of the square, side 6cm. Find the area of the shaded region.

  9. #109
    Executive Member seanieg89's Avatar
    Join Date
    Aug 2006
    HSC
    2007
    Gender
    Male
    Posts
    1,102
    Rep Power
    5

    Re: Cool problem of the day!



    Hopefully I didn't make a calculation error.
    Currently studying:
    PhD (Pure Mathematics) at ANU

  10. #110
    Senior Member qwerty44's Avatar
    Join Date
    Oct 2011
    HSC
    2013
    Gender
    Male
    Posts
    561
    Rep Power
    2

    Re: Cool problem of the day!

    Quote Originally Posted by seanieg89 View Post


    Hopefully I didn't make a calculation error.
    Correct.

  11. #111
    Moderator Carrotsticks's Avatar
    Join Date
    Jun 2009
    HSC
    N/A
    Gender
    Undisclosed
    Posts
    6,201
    Rep Power
    7

    Re: Cool problem of the day!

    Here's a question I posted a while ago but I don't remember if anybody answered it (don't think so). Best done by the interested and well-read HSC student.

    I am standing at the origin. I move to the right by one unit, then up by 1/2, then left by 1/3, then down by 1/4, then right again by 1/5 etc etc.

    If I continue this infinitely, is there a coordinate I will (eventually) reach? If so, what is it?

    ---------------------------------------

    Another:

    I am a 1-Dimensional person (so 1 degree of freedom). This means I can only either move forwards or backwards.

    I move forward 1 unit, then backward 1/2 units, then forward 1/3 units, then backwards 1/4 units etc etc.

    If I continue this infinitely, is there a coordinate I will (eventually) reach? If so, what is it?

    ---------------------------------------

    Another:

    Consider a regular n-gon. What is the total number of m-gons (not necessarily regular) that I can make such that m < n ? (careful about rotational symmetry).
    Bachelor of Science (Adv. Mathematics) - University of Sydney:

  12. #112
    Senior Member IamBread's Avatar
    Join Date
    Oct 2011
    HSC
    2011
    Gender
    Male
    Location
    UNSW
    Posts
    766
    Rep Power
    2

    Re: Cool problem of the day!

    Is the answer to the first one
    Last edited by IamBread; 19 Jun 2012 at 7:05 AM.
    Signature

  13. #113
    Moderator Carrotsticks's Avatar
    Join Date
    Jun 2009
    HSC
    N/A
    Gender
    Undisclosed
    Posts
    6,201
    Rep Power
    7

    Re: Cool problem of the day!

    Yep! Methinks that is a really cool result. No doubt if you could the first, then the second is trivial. Try going up 1 more dimension to 3D.
    Bachelor of Science (Adv. Mathematics) - University of Sydney:

  14. #114
    Senior Member IamBread's Avatar
    Join Date
    Oct 2011
    HSC
    2011
    Gender
    Male
    Location
    UNSW
    Posts
    766
    Rep Power
    2

    Re: Cool problem of the day!

    Yeah, and it was a lot of fun to do too. I am doing the first one now, so far got the z direction coordinate to be
    Signature

  15. #115
    Premium Dovahkiin Fus Ro Dah's Avatar
    Join Date
    Dec 2011
    HSC
    2013
    Gender
    Male
    Posts
    241
    Rep Power
    2

    Re: Cool problem of the day!

    Quote Originally Posted by Carrotsticks View Post
    Consider a regular n-gon. What is the total number of m-gons (not necessarily regular) that I can make such that m < n ? (careful about rotational symmetry).
    I like this question. The hardest part is finding a closed expression for the sum that determines the number of m-gons. I think a good Extension 2 student should be able to do so if they play around a bit with Complex Numbers. I will post a solution later if nobody else does.

  16. #116
    Premium Dovahkiin Fus Ro Dah's Avatar
    Join Date
    Dec 2011
    HSC
    2013
    Gender
    Male
    Posts
    241
    Rep Power
    2

    Re: Cool problem of the day!

    Quote Originally Posted by qwerty44 View Post


    The curves are arcs of circles whose centers are vertices of the square, side 6cm. Find the area of the shaded region.
    I know this question can be done by elementary means by partitioning various areas, but is it possible to evaluate it using calculus?


  17. #117
    Moderator Carrotsticks's Avatar
    Join Date
    Jun 2009
    HSC
    N/A
    Gender
    Undisclosed
    Posts
    6,201
    Rep Power
    7

    Re: Cool problem of the day!

    Pretty sure it can be done using the transformation formula you have there (by perhaps mapping it out to a triangular domain) but then you would need to find the points of intersections etc, which would be quite tedious.
    Bachelor of Science (Adv. Mathematics) - University of Sydney:

  18. #118
    Senior Member qwerty44's Avatar
    Join Date
    Oct 2011
    HSC
    2013
    Gender
    Male
    Posts
    561
    Rep Power
    2

    Re: Cool problem of the day!

    Found a pretty good one that most 2U students should try.


    Find the area of the rectangle.
    Attached Images Attached Images

  19. #119
    Moderator Carrotsticks's Avatar
    Join Date
    Jun 2009
    HSC
    N/A
    Gender
    Undisclosed
    Posts
    6,201
    Rep Power
    7

    Re: Cool problem of the day!

    Nice!
    Bachelor of Science (Adv. Mathematics) - University of Sydney:

  20. #120
    Executive Member bleakarcher's Avatar
    Join Date
    Jul 2011
    HSC
    2013
    Gender
    Male
    Posts
    1,479
    Rep Power
    2

    Re: Cool problem of the day!

    Quote Originally Posted by qwerty44 View Post
    Found a pretty good one that most 2U students should try.


    Find the area of the rectangle.
    Is it sqrt(3)?

  21. #121
    Exalted Member deswa1's Avatar
    Join Date
    Jul 2011
    HSC
    2012
    Gender
    Male
    Posts
    2,253
    Rep Power
    3

    Re: Cool problem of the day!

    Interesting one for a 4U student that I saw in one of our school's past papers:


  22. #122
    Senior Member qwerty44's Avatar
    Join Date
    Oct 2011
    HSC
    2013
    Gender
    Male
    Posts
    561
    Rep Power
    2

    Re: Cool problem of the day!

    Quote Originally Posted by bleakarcher View Post
    Is it sqrt(3)?
    That's what i got, but I don't have answer lol

  23. #123
    Executive Member bleakarcher's Avatar
    Join Date
    Jul 2011
    HSC
    2013
    Gender
    Male
    Posts
    1,479
    Rep Power
    2

    Re: Cool problem of the day!

    Quote Originally Posted by deswa1 View Post
    Interesting one for a 4U student that I saw in one of our school's past papers:

    I remember doing this a while ago now.

    k=2/3

  24. #124
    Senior Member qwerty44's Avatar
    Join Date
    Oct 2011
    HSC
    2013
    Gender
    Male
    Posts
    561
    Rep Power
    2

    Re: Cool problem of the day!

    Here is another good one:


    The lengths of the sides of the octagon are 1, 2, 3, 4, 5, 6, 7 and 8 units in some
    order. Find the maximum area of the hexagon (square units).

  25. #125
    Senior Member qwerty44's Avatar
    Join Date
    Oct 2011
    HSC
    2013
    Gender
    Male
    Posts
    561
    Rep Power
    2

    Re: Cool problem of the day!

    Quote Originally Posted by bleakarcher View Post
    Is it sqrt(3)?
    Yeh sqrt(3) confirmed.

Page 5 of 6 FirstFirst ... 3456 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •