Dan Piponi
Reputation
2,485
Top tag
Next privilege 2,500 Rep.
Create tag synonyms
 Apr 25 awarded Nice Answer Apr 21 comment Formal Proof that $f^{-1} \circ f = id_x \ , \forall f$ On your second line you have an expression on the left side of an implication and a proposition on the right. Mar 31 answered Quantum Mechanics Project Ideas!!! Mar 31 comment Number of ways to color paired shoes so that each pair will have different color In the case where three pairs are differently coloured, I think you might not have counted the way you can colour the remaining pair (both of which will have the same colour). Mar 29 comment Differing graphs for simple inverse exponential problem The problem is that there are 9 9th roots of any non-zero number. For positive numbers there's an obvious one that stands out. For negative numbers it's not clear which one you should pick. The real one (like Desmos did) or the first one you meet as you walk anticlockwise around the circle starting at a positive real number (as Mathematica does). Mar 29 comment Differing graphs for simple inverse exponential problem The meaning of the -1/9-th power of a negative number is up for debate. However, I think Google is just plain wrong here :-( Mar 29 comment Gradient of Function If the $x_i$ and $r_i$ are vectors, it's not clear what $(x_i-r_j)^3$ means. What do you mean by the cube of a vector? Mar 29 comment Is $\sqrt{-x^2-\frac{1}{x}}$ a rational function? It's not good enough just to say there can't be a square root. The term inside the square root needs not to be a perfect square. Mar 29 comment Ordinal numbers Yes. See section 5.5 of Nick Higham's book on mathematical style: books.google.com/… Mar 29 answered On the definition of exponential function Complex analysis Mar 29 comment very basic probability question Did you mean you choose three balls, one from each box? Mar 29 comment Fast algorithm to recognize sortable sequences Mar 29 answered Can every function be represented as polynomial Mar 28 answered Derivatives of nested/iterated functions. Mar 28 comment Derivatives of nested/iterated functions. "spiked"? Maybe you meant to type "piqued". Mar 24 comment If ${X_n} < \infty$, then $\sup {X_n} < \infty$, True or False? What range does $n$ live in? Mar 21 answered Opposite category trivial example Mar 21 answered A unit in $\mathbb{Z}_{9}[x]$ Mar 10 answered If two definite integrals are equal, does there exist a chain of substitutions and/or partial integrations which will get us from one to the other? Feb 24 comment What are some algorithms that can be used to test if a number is transcendental or not? If you're talking about real numbers represented as a stream of digits, say, being transcendental is not a computable property. Any transcendental number is within $\epsilon$ of a number that isn't transcendental so whatever decision you make, carrying on and reading more digits from the stream could change your decision. Having said that, read en.wikipedia.org/wiki/… for a practical algorithm that can find approximate "small" polynomial equations satisfied by reals.