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 Aug 8 comment How many circles are needed to cover a rectangle? @Fabian Yup, I am more interested in how to approach these problems. Aug 4 comment $L_{2}$ norm of the gradient of a vector valued function. You are correct, Silly me. Sorry for the bother. Aug 4 comment $L_{2}$ norm of the gradient of a vector valued function. Yeah I meant that too, I was talking about its norm. Aug 4 comment $L_{2}$ norm of the gradient of a vector valued function. @Brhn What is the context of the problem? Is there any more information you can provide? Aug 4 comment $L_{2}$ norm of the gradient of a vector valued function. I know your answer is assuming things due to lack of information from the OP, but as I guess the the "gradient" is basically a jacobian matrix between the two sets of variables and hence its norm must be the Frobenius norm or a spectral norm of a matrix. I am not sure though. Aug 4 comment Solving $x^4-y^4=z^2$ @Brhn Please accept the answer if the answer is correct and you are satisfied with it, else please let us know if you have some more doubts. Aug 4 comment 'Linux' math program with interactive terminal? @Magpie Its QtOctave Aug 4 comment Additive quotient group $\mathbb{Q}/\mathbb{Z}$ is isomorphic to the multiplicative group of roots of unity I will say every $\mathbb{Q/Z}$ is isomorphic to $X = \left\{x : x \in [0,1] \text{ and }x \in \mathbb{Q} \right\}$ Aug 4 comment Boundedness in a topological space? If you have found the answer helpful and correct, please accept it else let people know what more do you want from the answer. :-) Aug 3 comment Prove that $(n+\sqrt{n^2 -1})^k$ will always be of the form$(t+\sqrt{t^2 -1})$ where $n$, $k$, $t$ are natural numbers @RajeshKSingh: Do you remember where you found it? There might be something more to it. Aug 2 comment What is a good complex analysis textbook? @ChangweiZhou: Seriously man? In high school? Swell! Aug 2 comment Show $\lim_{h \to 0} \frac{f(h)+f(-h)}{h^2}=f''(0)$ @Ranabir: Yes, you can write $f''(0)=\lim_{h \to 0} \frac{f'(0)-f'(-h)}{h}$. This is because, $f''(0)$ is said to exist only when both the right and left hand limits exists and are equal to each other. Aug 2 comment Solving for $v$ in $v'(t) + R(t)\cdot v^{2/3}=J(t)$ @LeoIzen: $R(t)$ is a constant? Aug 2 comment Solving for $v$ in $v'(t) + R(t)\cdot v^{2/3}=J(t)$ I edited your answer to make the hyperlinks appear pretty so that it is easier to read and does not take focus away from your answer. :-) Aug 2 comment What does “$f$ is a function on $S$” mean? I am guessing the exact expression of $f$ will provide image. Aug 2 comment What does “$f$ is a function on $S$” mean? $S$ is a domain. The codomain is any superset of the image of $S$ under $f$. Aug 2 comment Is this a function? Thanks for that. :-) +1 Aug 2 comment Is this a function? @HenningMakholm: Okay, thanks. I was not aware of this notation. So you are saying the notation is equivalent to the below? $$\theta(x,y) = (3y,2x,x+y)$$ Aug 2 comment Is this a function? @Mathh Pressland: I do not believe the co-domain is $\mathbb{R}^{3}$, rather I believe the co-domain is a vector space $W$ where an element of $W$ is $w$ of the form $(u,v)$ where $u \in \mathbb{R}^{2}$ and $v \in \mathbb{R}^{3}$. This space might be isomorphic to $\mathbb{R}^{3}$ though. Aug 2 comment Is this a function? Yes, it is a function. Domain is $\mathbb{R^{2}}$ and co-domain is $V\times W$ where $V$ is a vector space over $R$ of dimension $2$ and $W$ is a vector space over $R$ of dimension 3.