Flying to Germany from another country where the visa has been issued
Can I travel to Germany from a country different from the one I got the visa from?
Let $X$ be a topological space. The diagonal of $X \times X$ is the subset $$D = \{(x,x)\in X\times X\mid x \in X\}.$$   Show that $X$ is Hausdorff if and only if $D$ is closed in $X \times X$.   First, I tried to show that $X \times X \setminus D$ is open using the fact that $X \times X$ is Hausdorff (because $X$ is Hausdorff), but I couldn't find an open set that contains a point outside $D$ and is disjoint to it... Get in vs. get on Possible Duplicate:          I'm an EFL (English as a foreign language) teacher and I haven't been able to come up with a good principle for which preposition to use after get when referring to transportation.  Some examples:   Get in:   a car/taxi/van/truck, etc.  Get on:   a bus/plane/bike/truck, etc.    How can one choose whether to use in or on? Note that in some cases, such as the example with truck, either preposition is possible but the choice affects the meaning.  I've been telling my students that there is no rule, so they just have to memorize which preposition to use, but I'm really hoping I'm wrong.  This question would be better suited for the upcoming  Stack Exchange, but it hasn't entered beta yet. More . How to calculate $\lim_{n\to\infty}(1+1/n^2)(1+2/n^2)\cdots(1+n/n^2)$? How can we compute the following limit:     $$\lim_{n\to\infty}(1+1/n^2)(1+2/n^2)\cdots(1+n/n^2)$$   Mathematica gives the answer $\sqrt{e}$. However, I do not know to do it. Picking a $\delta$ for a convenient $\varepsilon$? A few months ago I set full disk encryption during installation of Ubuntu 17.10. Now, I've decided to upgrade. The upgrade ran to the end without any problems. However, after reboot I am not able to log into my encrypted disk.  Where can be the problem? I am 100% sure I press the "right keys" on the keyboard, but technically I don't know what I am writing because of "*" characters and maybe after upgrade my keyboard layout changed. I use some characters which might be somewhere else on the keyboard. What language is default after upgrade?   By the way, I've already tried Caps-lock, but still no luck.  Help will be really appreciated. I am not a fan of installing my system and all backups over and over again. Schengen refusal formulae can be difficult to understand sometimes.    When an applicant receives a refusal with "Justification for the purpose and conditions of the intended stay was not provided", what does it mean? I'm trying to make a basic Windows application that builds a string out of user input and then adds it to the clipboard. How do I copy a string to the clipboard using Python? Infinite Series $\sum\limits_{n=1}^\infty\left(\frac{H_n}n\right)^2$ How can I find a closed form for the following sum? $$\sum_{n=1}^{\infty}\left(\frac{H_n}{n}\right)^2$$ ($H_n=\sum_{k=1}^n\frac{1}{k}$). There is this addon that was built called Window Generator 2. It can be . However, when I go to the download link it shows up in a new tab as a bunch of code.  How can I download and use this addon in Blender? The determinant of block triangular matrix as product of determinants of diagonal blocks I am given the following partitioned, upper-triangular matrix:  $$ \begin{bmatrix}   A_1 &amp;*  &amp;*  &amp;*  &amp;*  &amp;*  \\    0&amp; A_2 &amp;*  &amp;*  &amp;*  &amp;*  \\    .&amp;  0&amp; A_3 &amp;*  &amp;*  &amp;*  \\    .&amp;  0&amp;  0 &amp;...  &amp;*  &amp;. \\    .&amp;  0&amp;  0&amp;  0&amp; ... &amp;.  \\    0&amp;  .&amp;  ...&amp;  0&amp;0 &amp; A_m \end{bmatrix} $$  where each of the $A_i$ are block-matrices.  I have to prove that the determinant of this general matrix is: $$ \prod_{n=1}^m \det A_i. $$  We already proved in class that it is true for $ m=2 $ and we can use it in our proof.  Thanks for your answers! Is 'that is' optional? When I write something like this:     I am a man that is doing these things.   Is it correct to shorten it like this?     I am a man doing these things.   And does it require commas? When is $f=\left(\frac{\sqrt{p+4}}{1-p}-1\right)x^5-3x+\ln5$ decreasing $\forall\; x$? When is $$f=\left(\frac{\sqrt{p+4}}{1-p}-1\right)x^5-3x+\ln5$$ decreasing $\forall\; x$?    Diffrentiating: $$f'=5\left(\frac{\sqrt{p+4}}{1-p}-1\right)x^4-3$$ If $f$ is decreasing, $f'&lt;0$: $$5\left(\frac{\sqrt{p+4}}{1-p}-1\right)x^4-3&lt;0\implies x^4&lt;\frac3{5\left(\frac{\sqrt{p+4}}{1-p}-1\right)}$$ Since if $\left(\frac{\sqrt{p+4}}{1-p}-1\right)\to0^+\implies x^4&lt;+\infty$, which holds forallx, So:$$p=\frac{3\pm\sqrt{21}}2$$which doesn't ply with textbook-answer, since it mentions an domain for p. Complex Collision Boxes I'm trying to get a ball to go through in between the cup gear things shown in the screenshot below.   It seems that the collision box does not consider the cups. Yes, the ball fits and they are rotating in the right direction.  If there is already an answer to this, please link it.       If you have any questions about what is going on/ what the project is, feel free to ask. Normal subgroups of $S_4$ Can anyone tell me how to find all normal subgroups of the symmetric group $S_4$?  In particular are $H=\{e,(1 2)(3 4)\}$ and $K=\{e,(1 2)(3 4), (1 3)(2 4),(1 4)(2 3)\}$ normal subgroups? Find the image of (1,1,1) by T Question: Find the image of (1,1,1) by T  $$T(x,y,z) = (y,6y,x+y+z)$$   I found the standard matrix to be:   \begin{bmatrix}0&amp;1&amp;0\\0&amp;6&amp;0\\1&amp;1&amp;1\end{bmatrix}  I'm confused on how to approach this question.   In order to find the image is it possible to inverse the values of it's standard matrix?  Would I able to use the identity matrix of 3 and inverse the values of that to find the image?    Any help will be greatly appreciated. Prove continuous functions $f$ and $g$ are equal What is a "Swap Area"? So I noticed this question has not been asked directly;  What is this "Swap Area" people keep referring to when it comes to installing Ubuntu? How variance is defined? I'm in first year. Our class is in lesson " Heat and Thermodynamics". While solving a numerical problem of a reversible engine he told us that 100 degree Celsius is equal to 100 kelvin. I inquired but could not get satisfactory answer. Pleas help me understand it.  Here is the numerical, please consider it: A reversibe engine works between two temperatures whose difference is 100c. If it absorbs 746J of heat from the source and rejects 546J to the sink, calculate the temperature of the source and the sink. Ans (100°C, 0°C) Email to salesforce error While sending an attachment as an email to be attached to the salesforce record.Salesforce is giving the below given error.  Generating server: mx1.madison.gov  6-2j26dncatawfg1112dv2uwxupq9hzfgmjrrlrn2rx48cxm93nt.8-dea8eae.c.le.salesforce.com mx1-asg.mta.salesforce.com # #SMTP#  Is this salesforce problem or it is the Internal company server problem as I could see that error mentions company server name also.But to me doesn't look like company server error.