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General Q&A about all branches of theoretical and applied mathematics, including closely-adjacent sciences where the central question is about the math.

342 posts   RSS
Activity Age Score Random
Filters (None)
71%
+3 −0
Maximize Independent Variable of Matrix Multiplication

1 answer  ·  posted 2y ago by Josh Hyatt‭  ·  edited 2y ago by Josh Hyatt‭

matrices vector
50%
+0 −0
Why does the Dottie number $=\sqrt{1-\left(2\text I^{-1}_\frac12\left(\frac12,\frac32\right)-1\right)^2}$?

0 answers  ·  posted 2y ago by Tyma Gaidash‭  ·  edited 2y ago by Tyma Gaidash‭

probability equation median inverse
50%
+1 −1
Why $\color{red}{k\dbinom{k}{1}} \neq$ "first choose the k team members and then choose one of time to be captain"?

1 answer  ·  posted 3y ago by DNB‭  ·  edited 2y ago by Wolgwang‭

probability
25%
+0 −4
Why "only 1/10,000 men with wives they abuse subsequently murder them" ≠ P(A|G,M) & "50% of husbands who murder their wives abused them” ≠ P(G|A)?

0 answers  ·  posted 3y ago by DNB‭

probability
50%
+0 −0
If Alice must've have classes on at least 2 days, why do you need the intersection of 3 $A_i^C$'s? [closed]

0 answers  ·  posted 3y ago by DNB‭  ·  edited 2y ago by DNB‭

probability
28%
+0 −3
What is topology? When a person should learn it? [closed]

0 answers  ·  posted 2y ago by deleted user  ·  closed 2y ago by Peter Taylor‭

topology soft-question
28%
+0 −3
Intuitively, if you pick k out of n objects singly without replacement, why's the number of possible outcomes NOT $n(n-1) \dots [(n-(k - 1)]\color{red}{(n - k)}$?

1 answer  ·  posted 3y ago by DNB‭  ·  edited 3y ago by DNB‭

probability
40%
+0 −1
Notation for Euclidean Norm

1 answer  ·  posted 3y ago by Guilherme Costa‭  ·  last activity 3y ago by tommi‭

notation
75%
+4 −0
Intuitively, why's X% of Y = Y% of X?

1 answer  ·  posted 3y ago by Chgg Clou‭  ·  last activity 3y ago by celtschk‭

percentage
50%
+0 −0
How to derive some trigonometric formulas?

2 answers  ·  posted 3y ago by deleted user  ·  last activity 3y ago by deleted user

trigonometry
33%
+0 −2
Does "both girls, ≥ 1 winter girl" = "both girls, ≥ 1 winter child" let you generalize the problem statement that postulated both children as girls?

0 answers  ·  posted 2y ago by DNB‭  ·  edited 2y ago by DNB‭

probability
50%
+2 −2
What story and one-digit Natural Numbers explain Bayes' Theorem chart most simply?

0 answers  ·  posted 3y ago by DNB‭  ·  edited 3y ago by Moshi‭

probability
50%
+0 −0
How does the change of variable $\color{red}{r↦n−r}$ transmogrify $\sum\limits_{r=0}^n2^{n-r}\binom{n+r}{n}=2^{2n}$ into $\sum\limits_{k=0}^{n} \frac{\binom{2n-k}{n}}{2^{2n-k}}=1$?

1 answer  ·  posted 3y ago by DNB‭  ·  edited 3y ago by Moshi‭

summation
50%
+0 −0
"A occurred" vs. "something must happen"

1 answer  ·  posted 3y ago by DNB‭  ·  edited 3y ago by DNB‭

probability
71%
+3 −0
Why would skyrocketing the numbers of doors help laypeople intuit the Monty Hall Problem?

1 answer  ·  posted 3y ago by DNB‭  ·  edited 2y ago by DNB‭

probability
37%
+1 −3
If money's less valuable in the two-bullet case of the Russian Roulette problem, then ought you pay more to remove a bullet when the gun has $\ge 2$ bullets?

0 answers  ·  posted 3y ago by Chgg Clou‭

probability
60%
+1 −0
What it ≡ called?

1 answer  ·  posted 2y ago by Anonymous‭  ·  last activity 2y ago by Quintec‭

symbols
71%
+3 −0
Find limits of integration in polar coordinates

2 answers  ·  posted 2y ago by MissMulan‭  ·  last activity 2y ago by r~~‭

calculus double-integrals polar
60%
+1 −0
differentiate under integral sign says something went wrong

1 answer  ·  posted 3y ago by deleted user  ·  last activity 3y ago by celtschk‭

calculus multivariable-calculus differentiation integration improper-integral
50%
+1 −1
Acceptable, usual to write $\ge 2$ pipes simultaneously?

1 answer  ·  posted 2y ago by DNB‭  ·  last activity 2y ago by Derek Elkins‭

probability
60%
+1 −0
What does upper indices represent?

2 answers  ·  posted 2y ago by deleted user  ·  last activity 2y ago by r~~‭

notation tensors
33%
+0 −2
If k = 1, why $n(n-1) \dots \color{red}{(n-k+1)} = n$?

1 answer  ·  posted 3y ago by DNB‭  ·  edited 3y ago by DNB‭

probability
50%
+0 −0
How does $P(C > D \mid C = 2) \neq P(C > D \mid C \neq 2)$ prove that B > C depends on C > D?

0 answers  ·  posted 2y ago by DNB‭  ·  edited 2y ago by DNB‭

probability
57%
+2 −1
If $n = xm$ and $n \rightarrow \infty$, then $m \rightarrow \infty$?

1 answer  ·  posted 3y ago by TextKit‭  ·  last activity 3y ago by The Amplitwist‭

calculus
33%
+0 −2
Why's the unique sub-game perfect equilibrium, that the first player should offer around $1.25 to player 2?

0 answers  ·  posted 3y ago by Chgg Clou‭

game-theory
33%
+0 −2
Why's the true positive rate termed Sensitivity and true negative rate Specificity, not vice versa? [closed]

0 answers  ·  posted 3y ago by DNB‭  ·  closed 2y ago by Peter Taylor‭

probability
57%
+2 −1
Why rational to be indifferent between two urns, when urn A has 50-50 red and white balls, but you don't know urn B's ratio?

2 answers  ·  posted 3y ago by Chgg Clou‭  ·  last activity 3y ago by celtschk‭

probability
33%
+0 −2
What story and two-digit Natural Numbers best fit Bayes' Theorem chart?

0 answers  ·  posted 3y ago by DNB‭  ·  reopened 3y ago by Monica Cellio‭

probability
50%
+0 −0
Why mustn't the proportion of smokers among married people be the same as the proportion of smokers in the whole population?

1 answer  ·  posted 3y ago by Chgg Clou‭  ·  last activity 3y ago by r~~‭

probability
71%
+3 −0
Are we in a "history-valley" for Topology?

2 answers  ·  posted 2y ago by whybecause‭  ·  last activity 2y ago by Derek Elkins‭

topology history-philosophy-of-math
60%
+1 −0
How $ijk=\sqrt{1}$?

2 answers  ·  posted 2y ago by deleted user  ·  last activity 2y ago by Tim Pederick‭

quaternions
83%
+8 −0
Are there useful topologies on Cartesian products “in between” the product topology and the box topology?

0 answers  ·  posted 3y ago by celtschk‭  ·  edited 3y ago by celtschk‭

topology
40%
+0 −1
What is the meaning of integration under integral sign?

1 answer  ·  posted 3y ago by deleted user  ·  last activity 3y ago by deleted user

calculus integration
50%
+0 −0
How to intuit : married smokers × all people < all smokers × all married people ?

0 answers  ·  posted 3y ago by Chgg Clou‭

probability
33%
+2 −6
Can we add without using addition?

3 answers  ·  posted 2y ago by General Sebast1an‭  ·  last activity 2y ago by DavidCary‭

equation arithmetic
28%
+0 −3
Are Stars and Bars in Combinatorics related to the Fence Post Error?

0 answers  ·  posted 3y ago by DNB‭

combinatorics
28%
+0 −3
If a repair on a vessel costs $2$ and fully repaired vessel is worth $1$, don't we need know worth of broken vessel to decide whether to repair?

0 answers  ·  posted 3y ago by Chgg Clou‭  ·  edited 2y ago by Wolgwang‭

basic
50%
+0 −0
"the people who move have a percentage of Democrats which is between these two values" — How does this furnish intuition for Simpson's Paradox?

0 answers  ·  posted 2y ago by DNB‭  ·  edited 2y ago by DNB‭

probability
33%
+0 −2
Why 1. multiply the number of independent options? 2. add the number of exclusive options?

3 answers  ·  posted 2y ago by DNB‭  ·  last activity 2y ago by Tim Pederick‭

probability
50%
+0 −0
How does $\lim\limits_{n \to \infty} \dfrac{p[s + (1 - s)c^n]}{p[ s + (1 - s)c^n] + (1 - p)[s + (1 - s)w^n]} = p?$

1 answer  ·  posted 3y ago by DNB‭  ·  last activity 3y ago by r~~‭

limits
33%
+0 −2
You're sampling k people from a population of size n one at a time, with replacement and with equal probabilities. Order or not?

0 answers  ·  posted 3y ago by DNB‭

probability
50%
+0 −0
Solve $\int_0^{\dfrac{\pi}{6}} \sec^3 \theta \mathrm d\theta$

1 answer  ·  posted 3y ago by deleted user  ·  last activity 3y ago by deleted user

calculus integration definite-integrals
75%
+4 −0
Proving the Equation of the Pencil of Two Intersecting Circles

1 answer  ·  posted 3y ago by TripleFault‭  ·  last activity 3y ago by msh210‭

high-school-mathematics pencil conics proof circle
40%
+0 −1
$\int dx dy dz d p_x dp_y dp_z$ Does it have any physical meaning?

1 answer  ·  posted 2y ago by deleted user  ·  last activity 2y ago by r~~‭

integration line-integral integral
40%
+0 −1
If A & B are joint, can Arby recoup some of his loss only when $P_{Arby}(A \cup B) < P_{Arby}(A) + P_{Arby}(B)$?

0 answers  ·  posted 3y ago by DNB‭  ·  edited 2y ago by DNB‭

probability
42%
+1 −2
How can I visualize $\lim\limits_{x \rightarrow \pm \infty} f(x) = \lim\limits_{t \rightarrow 0^{\pm}} f(1/t)$?

1 answer  ·  posted 3y ago by TextKit‭  ·  last activity 3y ago by thelast19digitsofpi‭

visualization
40%
+0 −1
What to do when there's lot of function of time? (For integration) Should I consider them as constant?

1 answer  ·  posted 2y ago by deleted user  ·  last activity 2y ago by r~~‭

integration
33%
+1 −4
How can you "easily see that such squares [of side length $\sqrt{13}$ and $\sqrt{18}$] will not fit into the [4 × 4] grid"?

1 answer  ·  posted 2y ago by DNB‭  ·  last activity 2y ago by Tim Pederick‭

geometry
42%
+1 −2
In $w_{k + 1} - w_k = (\frac{1 - p}{p})^{exponent}(w_1 - w_0)$, why isn't exponent $k + 1$?

1 answer  ·  posted 3y ago by DNB‭  ·  last activity 3y ago by leovt‭

probability
37%
+1 −3
How can I generalize a picture for the Mean Value Theorem to the Generalized MVT?

1 answer  ·  posted 3y ago by TextKit‭  ·  edited 3y ago by TextKit‭

calculus visualization
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