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9h
comment Discrete math of $i^3$
@Uncountable: There's some irony in someone with that username suggesting the use of induction. :-)
9h
comment Infinite dimensional vector space
Does $\mathbb R \ncong \mathbb C$ also hold if you only consider the vector space structure over $\mathbb Q$? Because if you consider additional structure, then also $\mathbb C$ and $\mathbb R^2$ are not isomorphic, but as real vector spaces they are.
9h
answered If $ f $ is injective and $ g $ is injective, then $ f \circ g $ is surjective.
18h
comment Can we have a one-one function from [0,1] to the set of irrational numbers?
@user21820: What exactly do you think I have to justify? That $\pi$ is transcendental is a well-known fact; see e.g. Wikipedia.
18h
answered Can we have a one-one function from [0,1] to the set of irrational numbers?
1d
awarded  Vox Populi
1d
comment math question that I can't figure out.
Depends on how you define the pattern. There is the one pattern that the one asking the question probably had in mind, but it could just as well be the values of the polynomial $p(x)=\frac16x^3-\frac12x^2+\frac43x$ at $x=1,2,3,4,\ldots$. In which case in the fifth week he'd save \$15, and in the sixth week, he'd save \$26.
1d
comment Is $f:\mathbb{Q^*} \rightarrow \mathbb{Q}$ by $f(\frac{a}{b}) = \frac{\max{(a,b)}}{\min{(a,b)}}$ a function?
What are the possible values of $a$ and $b$? In particular, can $b$ be negative?
1d
comment Is there fundamental goal of mathematics?
Does this qualify?
1d
revised Is there fundamental goal of mathematics?
Corrected spelling of Gödel
1d
comment Unit that is distance times time?
Isn't that a question for physics.SE?
1d
comment please solve this loop
How is this question related to calculus?
1d
reviewed Approve A continuous bijection from the Cantor set to the open interval $(0,1)$.
1d
comment Intersection of two sets which are equivalence on set A is always equivalence?
@Sharma: A relation is a set. See my answer.
1d
revised Intersection of two sets which are equivalence on set A is always equivalence?
added 120 characters in body
1d
answered Intersection of two sets which are equivalence on set A is always equivalence?
1d
comment sets union problem
How can the union of two non-empty sets (number of elements $>0$ for each one) be empty (number of elements$=0$)? And while the maximum is correct, the condition is clearly wrong there, too.
1d
revised Give an example to show that convergence of $|x_n|$ does not imply the convergence of $x_n$
added 369 characters in body
1d
answered Give an example to show that convergence of $|x_n|$ does not imply the convergence of $x_n$
1d
answered What does it mean for two matrices to be orthogonal?