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Aug
19
answered What happens if the coefficients of polynomials are not taken from a field of real numbers?
Aug
3
comment Calculate the width and height of a rectangle, given its diagonal and area
you have all the information to compute what $(x+y)^2$ is. Therefore you can compute $x+y$, and deduce the perimeter. You don't need to find out what $x$ and $y$ are, knowing $x+y$ is enough.
Aug
2
answered Calculate the width and height of a rectangle, given its diagonal and area
Jul
24
comment Bijection between $\mathbb N^+ \times \mathbb R^+$ and $\mathbb R^+$
You just need bijections $\mathbb N\to \mathbb N^+$ and $\mathbb R^+\cup\{0\}\to \mathbb R^+$ (and the first gives the second by the way).
Jul
24
comment Bijection between $\mathbb N^+ \times \mathbb R^+$ and $\mathbb R^+$
it depends if "bigger" in the question means strictly bigger or $\geq$. Anyway it is not hard to go from one to the other with bijections.
Jul
24
answered Bijection between $\mathbb N^+ \times \mathbb R^+$ and $\mathbb R^+$
Jul
23
comment A game with checkers
I corrected after the comment
Jul
23
revised A game with checkers
added 77 characters in body
Jul
23
revised A game with checkers
added 77 characters in body
Jul
23
revised A game with checkers
added 123 characters in body
Jul
23
answered A game with checkers
Jul
20
comment (In)Completeness: First Order x Second Order
you should maybe precise that you are talking about proof systems, not to be confused with for instance incompleteness of first-order Peano arithmetic.
Jul
19
comment Showing that $A\rightarrowtail A \times \{x\}$ is a bijection
you probably mean $A\times\{x\}$
Jul
18
comment Some examples of applications of Game Theory
not specifically, try to explore...
Jul
18
comment Interview riddle
yes it is 6, I just increased the size.
Jul
18
revised Interview riddle
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Jul
18
comment Some examples of applications of Game Theory
if you are looking for open problems from game theory, then there are a lot. Some are accessible at highschool levels, as many games have not been studied extensively, so a project could be to take a game that is not too well-known (you can even invent one), and study it from a game-theoretic point of view, then present your result at the science fair.
Jul
18
comment Proof needed for this exercise from “Linear Algebra Done Right”
taking basis is always a good start with finite-dimensional vector spaces
Jul
18
comment Why is this definition of complex numbers “informal”?
@DavidK Then what you are doing is putting new constant and axioms in mathematics, so you don't work in ZFC anymore (or the system you worked with), but in "ZFC+some axioms about i", which is formal but not really what we want to do.
Jul
18
revised Some examples of applications of Game Theory
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