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1d
awarded  Good Answer
Sep
20
awarded  Nice Question
Sep
16
awarded  Yearling
Sep
10
awarded  Nice Answer
Sep
4
answered Proof of trigonometric identity $\cot \theta \sec\theta= 1/ \sin\theta$
Jul
31
awarded  Notable Question
Jul
28
comment Is every factorial divisible by its sum of digits?
@G.H.Faust: Add it to OEIS!!
Jul
27
comment Is every factorial divisible by its sum of digits?
what about sum of binary digits? (following the usual observation that there's nothing special about 10)
Jul
7
revised Converting recursive equations into matrices
typos
Jul
2
awarded  Curious
Jun
28
comment How to define the disciplines of mathematics
Everything is both similar and different from everything else. The general ideas of the above three categories solidify around their respective centers, but they cross over quite a bit.
Jun
6
comment 'Obvious' theorems that are actually false
For #4, the restriction where this _does work are given by the Fubini-Tonelli theorem
Jun
6
comment Why does differentiating a polynomial reduce its degree by $1$?
Nice... this is Sturm's theorem
Jun
6
comment Generalised Binomial Theorem Intuition
"why don't they teach it in secondary school?" - That's what math.SE is for.
Apr
10
comment (k+1)th, (k+1)st, k-th+1, or k+1?
Also, the ordinal for 301 is pronounced "three hundred and first".
Apr
8
awarded  Nice Answer
Mar
27
comment Why use *λx.x* instead of *f(x)*?
One could also ask then why don't we use '(x)f' instead of 'f(x)' (postpositioning the function name makes it easier to interpret composition of functions in a left to right reading.
Mar
21
awarded  Nice Question
Mar
7
comment What is exponentiation?
It all depends on what you mean by 'mean'. If it is simply a matter of "I don't get it" despite being able to do the manipulations, one could say that there is no intention of you to 'get it', it just a mindless preservation of the rules for basic exponentiation (which I think you do 'get') to allow some calculation. If 'mean' means "I don't see a quick generalization that encompasses integers and reals" then the best generalization is to complex numbers and scaling rotation. (hmm, that doesn't explain it for reals though...OK stick with the calculus/derivative equals itself.)
Mar
5
comment Does there exist a system such that the additive identity is non-zero?
In the semiring of languages (sets of strings), union of two languages acts like addition, and the additive identity is the empty set. Multiplication is string concatenation (well a little more complicated than just that) and the multiplicative identity is the empty string.