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University of Florence


Jun
11
answered Is there a parametric form for a degenerate conic section?
Jun
11
comment Solve set problems without Venn diagrams
@AsafKaragila I would say that combinatorics is based on set theory... I cannot imagine an axiomatization of combinatorics which does not use sets. Instead I can imagine an axiomatization of numbers (real or natural) without sets.
Jun
11
revised Solve set problems without Venn diagrams
added 371 characters in body
Jun
11
comment Solve set problems without Venn diagrams
I would say no: because the statement of the problem itself can only be modeled by using sets. A purely algebraic solution cannot explain why the formula used is true.
Jun
11
answered Solve set problems without Venn diagrams
Jun
11
comment How to find the number of possible permutations in a composition function
You found $khk = h^3$. Multiply both sides of equation by $k$ on the right to obtain: $khkk = h^3 k$. But you know that $kk=1$ hence you obtain $kh = h^3 k$. About $kh^3 = kh$ you can multiply on the left by $k$ and obtain $h^3 = h$ which becomes $h^2=1$ which is false.
Jun
11
answered Differentiability of $f(x) = x \sin \frac{1}{x}$ for $x \neq 0$ and $0$ for $x = 0$.
Jun
11
comment How to find the number of possible permutations in a composition function
I don't use any theorem, just some algebraic computation. What is not clear?
Jun
11
revised How to find the number of possible permutations in a composition function
added 444 characters in body
Jun
11
answered How to find the number of possible permutations in a composition function
Jun
2
awarded  Revival
May
30
comment Is $e^{i\pi}+1=0$ all it's cracked up to be?
$e^{i\tau} = 1$
May
30
comment Prove $ \int_{C}fdr=\int_{S}dS\times\nabla f$
$f$ is a scalar function? The integral on the left seems to be a scalar value while the one on the right seems to be a vector...
May
30
revised Can I change determinant and partial derivation?
added 217 characters in body
May
30
answered Can I change determinant and partial derivation?
May
30
answered Prove $ \int_{C}fdr=\int_{S}dS\times\nabla f$
May
28
answered Positive continuous function from a Non-negative continuous function on a Tychonoff space
May
27
revised Existence of a one-to-one function (injection) from one finite set to another
edited body
May
27
answered Existence of a one-to-one function (injection) from one finite set to another
May
27
answered How to prove $C\subseteq f^{-1}[f(C)]$?