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Forum: Challenge Questions and Puzzles

Have a challenging question or puzzle you want to share with the community? Post it here (homework questions do NOT belong here).

  1. Sticky Thread Sticky Threads

    • Replies: 2
    • Views: 1,912
    October 15th, 2017, 16:11 Go to last post
  1. Normal Thread Normal Threads

  2. Integral challenge

    Started by lfdahl, November 20th, 2017 17:58
    challenge, definite, integral, solve, theta
    • Replies: 5
    • Views: 119
    Today, 13:47 Go to last post
  3. Polynomial with five roots

    Started by lfdahl, November 12th, 2017 16:53
    $1$, equation, polynomial, product, roots
    • Replies: 1
    • Views: 77
    Yesterday, 17:30 Go to last post
  4. Sequence challenge

    Started by lfdahl, November 20th, 2017 18:32
    $n=1, constant, leftx_nright, sequence, show
    • Replies: 2
    • Views: 64
    Yesterday, 17:21 Go to last post
  5. Prove the sum identity

    Started by lfdahl, November 20th, 2017 18:13
    $sum_n=0^infty, fracn^2n=2e$, limit, prove, sum
    • Replies: 4
    • Views: 80
    November 21st, 2017, 09:06 Go to last post
  6. equivalence

    Started by solakis, July 18th, 2017 15:33
    book, equivalence, formal, maths, proofs
    • Replies: 2
    • Views: 101
    November 19th, 2017, 19:32 Go to last post
  7. Inequality

    Started by lfdahl, November 19th, 2017 17:36
    inequality, infty, limit, sum_i=1^nfrac1i^2, [lim_nrightarrow
    • Replies: 2
    • Views: 74
    November 19th, 2017, 17:59 Go to last post
  8. axiomatics

    Started by solakis, September 11th, 2017 19:35
    a+b=0vee, aa=bblongrightarrow, axiomatics, forall, prove
    • Replies: 2
    • Views: 151
    November 16th, 2017, 09:49 Go to last post
  9. proof in predicate calculus

    Started by solakis, December 23rd, 2016 16:03
    forall, neg, predicate, xin, yleftrightarrow
    • Replies: 2
    • Views: 188
    November 15th, 2017, 10:02 Go to last post
  10. Unsolved Challenge
    Prove √(sinx)>sin√(x)

    Started by anemone, October 15th, 2017 00:20
    $sqrtsin, √sinxsin√x, prove, sqrtx$, xsin
    • Replies: 2
    • Views: 189
    November 13th, 2017, 11:53 Go to last post
  11. Series challenge

    Started by lfdahl, November 2nd, 2017 17:12
    $frac14+frac48+frac812+, challenge, determine, series, sum
    • Replies: 3
    • Views: 137
    November 9th, 2017, 18:33 Go to last post
  12. A cube with 9 interior points

    Started by lfdahl, November 1st, 2017 17:51
    $frac12sqrtleft3right, $frac12sqrtleft3right$, cube, interior, points
    • Replies: 2
    • Views: 82
    November 8th, 2017, 10:58 Go to last post
  13. Inequality of Four Variables

    Started by anemone, July 29th, 2016 00:14
    $aba^2+, bcb^2+, b^2, c^2, prove
    • Replies: 1
    • Views: 267
    November 6th, 2017, 17:25 Go to last post
  14. Game on a chessboard

    Started by Evgeny.Makarov, February 14th, 2017 13:25
    game, john, move, peter, squares
    • Replies: 1
    • Views: 152
    November 6th, 2017, 17:22 Go to last post
  15. Derive a closed form and find its limit

    Started by lfdahl, November 4th, 2017 15:56
    $s_nk$, closed, find, form, limit
    • Replies: 6
    • Views: 145
    November 6th, 2017, 16:41 Go to last post
  16. triangular relations

    Started by solakis, October 17th, 2017 18:33
    ad^2+de^2+ae^2=, bd=de=ec, points, prove, triangular
    • Replies: 1
    • Views: 93
    November 6th, 2017, 16:07 Go to last post
  17. Unsolved Challenge
    Prove a quartic equation has at least one real solution

    Started by anemone, November 3rd, 2017 21:52
    equation, greater, prove, real, solution
    • Replies: 2
    • Views: 125
    November 5th, 2017, 01:42 Go to last post
  18. Unsolved Challenge
    Trigonometric Sum

    Started by greg1313, October 31st, 2017 00:20
    $n=3, prove, show, sum, trigonometric
    • Replies: 2
    • Views: 132
    November 3rd, 2017, 22:09 Go to last post
  19. Unsolved Challenge
    Trigonometric equality

    Started by anemone, October 26th, 2017 12:39
    $sin, equality, prove, sin, trigonometric
    • Replies: 1
    • Views: 163
    October 29th, 2017, 08:47 Go to last post
  20. Unsolved Challenge
    Evaluate tanē a + 2tanē b

    Started by anemone, October 23rd, 2017 12:05
    $b$, b+3cos, b+6cos, evaluate, sin
    • Replies: 5
    • Views: 250
    October 24th, 2017, 12:56 Go to last post
  21. Unsolved Challenge
    Prove (a-b)ᵃ⁻ᵇaᵃᵇ⁻ᵃ ≥ (a-1)ᵃᵇ⁻ᵇ

    Started by anemone, October 19th, 2017 11:38
    $a$, $b$, a-bᵃaᵃ, positive, prove
    • Replies: 0
    • Views: 89
    October 19th, 2017, 11:38 Go to last post
  22. sequences

    Started by solakis, October 1st, 2017 10:58
    1^n, diverges, prove, sequence, sequences
    • Replies: 8
    • Views: 289
    October 17th, 2017, 20:17 Go to last post
  23. Unsolved Challenge
    Evaluate ∠APR

    Started by anemone, October 14th, 2017 02:19
    $angle, apq=3angle, apr$, evaluate, triangle
    • Replies: 3
    • Views: 219
    October 15th, 2017, 04:16 Go to last post
  24. Trig Inequality

    Started by lfdahl, October 4th, 2017 17:21
    $$5x, 8sin, inequality, show, trig
    • Replies: 2
    • Views: 160
    October 14th, 2017, 15:40 Go to last post
  25. Find the maximal value of the sum

    Started by lfdahl, October 8th, 2017 14:36
    find, maximal, numbers, real, satisfying
    • Replies: 1
    • Views: 120
    October 14th, 2017, 15:22 Go to last post
  26. Unsolved Challenge
    Prove ∠A≤60°.

    Started by anemone, October 13th, 2017 12:28
    attempt, challenge, interesting, prove, unsolved
    • Replies: 2
    • Views: 176
    October 14th, 2017, 12:24 Go to last post
  27. TikZ Challenge 3 - Vector Diagram

    Started by I like Serena, September 26th, 2017 16:43
    challenge, create, picture, submission, tikz
    • Replies: 2
    • Views: 151
    October 9th, 2017, 11:04 Go to last post
  28. Find The Sum

    Started by lfdahl, October 3rd, 2017 14:16
    evaluate, find, sum
    • Replies: 2
    • Views: 155
    October 5th, 2017, 14:52 Go to last post
  29. Binomial sum

    Started by lfdahl, September 27th, 2017 15:41
    $$s_n, =sum_k=0^n-1^k3n, binomial, evaluate, sum
    • Replies: 2
    • Views: 153
    October 4th, 2017, 16:01 Go to last post
  30. Ratio of determinants

    Started by lfdahl, September 30th, 2017 15:31
    $$[beginvmatrix, c_k+1, c_k+2, determinants, ratio
    • Replies: 2
    • Views: 170
    October 3rd, 2017, 13:06 Go to last post
  31. proving a formula

    Started by solakis, September 28th, 2017 17:41
    axists, prove, proving, wedge, xin
    • Replies: 3
    • Views: 129
    September 30th, 2017, 11:15 Go to last post

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Top 84 Thread Starters For "Challenge Questions and Puzzles"

RankUser NamePercentage Of TotalThreadsMost Recent Thread
1anemone43.9745Prove a quartic equation has a...
2Albert21.1358find a,b
3lfdahl5.594Sequence challenge
4kaliprasad3.559find n
5ZaidAlyafey2.339Harmonic numbers identity
6MarkFL1.831Definite Integral
7Random Variable1.628A residue calculation
8sbhatnagar1.526Two Challenging Integrals
9jacks1.525Indefinite integration involvi...
10DreamWeaver1.424An inverse tangential problem
11caffeinemachine0.915MHB's First Polymath Project.
12Pranav0.813Summation challenge #2
13solakis0.712triangular relations
14Krizalid0.610Continuity of IVP
14Wilmer0.610Tuff Sequence...
14checkittwice0.610Determine all solutions in pos...
15greg13130.59Trigonometric Sum
15magneto0.59Sequence Challenge
16mathmaniac0.586n^3 + 3 is not a perfect 6th ...
16eddybob1230.58Increasing and Decreasing Numb...
17melese0.47Rational roots
17Rido120.47Find the limit (n!)^(1/n)/n
17hxthanh0.47Write n = a + b + c + ...
17mente oscura0.47Find the 6 reals roots
18CaptainBlack0.46Problem from Paper 3 of the 19...
18Bacterius0.46Divergence of a trigonometric ...
18soroban0.46The Missing intercept
18I like Serena0.46TikZ Challenge 3 - Vector Diag...
18mathbalarka0.46A double sum challenge
18mathworker0.46pigeon hole proof
18Shobhit0.46An Infinite product
18Fallen Angel0.46Find all functions
19Poirot0.35Co-prime challenge
19sadsadsadsa0.35Ricky's Dinner
19jacobi0.35Probability challenge
20Evgeny.Makarov0.24Game on a chessboard
20jakncoke0.24Putnam 2012: A5
20Theia0.24Differentiation challenge
21Also sprach Zarathustra0.23Integral of x^{-x}
21alane19940.23Einstein's Riddle
21Farmtalk0.23Secret Order
21The Lord0.23Integral
21Petrus0.23Differential Equation challeng...
22chisigma0.12A false approach to an integra...
22TheBigBadBen0.12Logic problem
22M R0.12Geometry Challenge
22Fermat0.12integration
22Euge0.12Abstract Algebra Challenge
22Illmatic0.12Sum of reciprocals of roots
22jmprada0.12Sphere diameter
23The Chaz0.11Travelers and coins
23Prove It0.11Challenge: Is cos(pi/60) trans...
23Alexmahone0.11Hourglasses
23tkhunny0.11Missing in NY/PA
23Sherlock0.11Sum involving pi, ln(2) and Ca...
23Fernando Revilla0.11lim x ⌊1 / x⌋ , x...
23HallsofIvy0.11A geometric puzzle
23masters0.11Where's the father?
23DrunkenOldFool0.11infinite sum
23Opalg0.11Puzzle with digits
23Deveno0.11Identify the mystery group
23Amer0.11Nice Puzzle
23princeps0.11LCM Inequality
23Chris110.11Simple, fun puzzle
23QuestForInsight0.11Exponential limit
23topsquark0.11Sort of a challenge
23Petek0.11Unique Factorization Domains
23mssrki0.11Mathematics - a new basis
23johng0.11number of p subgroups
23judytl30.11Factoring over the Integers
23stainburg0.11Boring. Then Prove it!
23jeffer vitola0.11Limit is Sum
23individ0.11Solve triple square Diophantin...
23RLBrown0.11Next integer in this sequence,...
23Bibubo0.11divisibility and sums
23maxkor0.11exactly one triple
23Dai0.11Puzzle
23Prakhar0.11Challenging Integral
23RobJob0.11The connected Game
23Monoxdifly0.11Arrange Mathematical Operation...
23Joppy0.11Show that is the square of an ...
23steevsaul0.11
23bio0.11Year 7 & 8 mathematics puz...
23rick1230.11The Durango Curve Problem
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