how to create child A from child B and cast to Parent?
Resolve build errors due to circular dependency amongst classes
Question concerning linear combinations of vectors and linear independence in Linear Algebra. C#: code error while changing the active directory user's password I have two systems installed previously Windows 7 and Ubuntu. I was trying to reinstall Ubuntu and format the Ubuntu OS partition using a tool in Windows 7.   When I have Ubuntu ready on a USB stick and restart my laptop, it prompts me with the GRUB rescue screen. If I boot from USB to install Ubuntu, it just hangs.   Anyway, I messed up everything. So my question is how can I boot Windows 7 now? I have lost functionality in the tool shelf. When I click on a selector or something in the bottom part of the tool self that you can hide and unhide, nothing happens. I can see the options but when I click it doesn't work. See screenshot where it says "Add Cylinder". Consider the space of continuously differentiable functions, $$C^1([a,b]) = \{f:[a,b]\rightarrow \mathbb{R}\mid f,f' \text{ are continuous}\}$$ with the $C^1$-norm $$\lVert f\rVert := \sup_{a\leq x\leq b}|f(x)|+\sup_{a\leq x\leq b}|f'(x)|.$$ Prove that $C^1([a,b])$ is a Banach Space.   This was the proof we were given: Assuming $C^1([a,b])$ is a normed linear space all we need to show is completeness. Let $(f_n)$ be a Cauchy Sequence in $C^1([a,b])$ with respect to the $C^1$-norm. Then each $f_n,f'_n\in (C([a,b]),\|\cdot\|_{\sup})$. We know that $C([a,b])$ is complete and thus there exists $f,g\in C([a,b])$ such that $f_n\rightarrow f$, and $f'_n\rightarrow g$ (uniformly) with respect to $\|\cdot\|_{\sup}$. If we let  $$ F_n(x) = \int_a^x f_n(t)dt, \hspace{2mm}  F(x) = \int_a^x f(t)dt $$ then $F_n\rightarrow F$ uniformly because  $$\lVert F_n-F\rVert_{\sup}\leq \sup_{a\leq x\leq b}\int_a^x|f_n(t)-f(t)|dt\leq \lVert f_n-f\rVert_{\sup}&lt;\epsilon.$$ From the fundamental theorem of calculus: $$f_n(x)-f_n(a) = \int_a^x f'_n(t)dt $$ Since $f'_n\rightarrow g$ uniformly then  $$ \int_a^xf'_n(t)dt\rightarrow \int_a^x g(t)dt $$ Since we know that $f_n\rightarrow f$ uniformly, $$f(x)-f(a) = \int_a^x g(t) dt $$ which by the fundamental theorem of calculues implies $f'=g$. So we know have $f_n\rightarrow f$ and $f'_n\rightarrow g=f'$ which mean $f_n\rightarrow f\in C^1([a,b])$ with respect to $C^1$-norm. So every cauchy sequence converges. Hence $C^1([a,b])$ is a Banach Space.   So I understand most of the proof. Where I get confused is that how did we actually show this satisfies the $C^1$-norm? Maybe I don't understand what this norm actually does.   Thank you for any help, comments and advice! How to insert strings containing slashes with sed? In electromagnetism, why does nature prefer the right-hand rule over the left-hand rule? Trying to put a footnote in subsection title:  \subsection{Effect of Lateral Confinement on SW Band Structure\footnote{Parts of this sub--section are based on \citet{Venkat2013}}}   produces the following error:  Argument of \@sect has an extra } ...section are based on \citet{Venkat2013}}}   I am using:   \documentclass[paper=A4, fontsize=12, toc=listof, toc=index, toc=bib]{scrreprt}   Please advise. Background Nowadays, I see &quot;them&quot; used to mean &quot;those&quot; a lot. I don't know if it was as common in the past. For example, take &quot;one of &quot;. On researching about it, I found some people say it comes from a dialect of British English. Some others say it is a &quot;non-standard&quot; usage. I see this usage in Canadian English also, and it seems some people use it in a sarcastic way. Moreover, I have seen a song titled &quot;one of them days&quot;. I also read, in the book called &quot;A Broken Promise&quot;, &quot;&quot; Finally, Wikipedia says that it is a usage in  (a common name for the Southern Midland dialect of American English):  Pronouns and demonstratives &quot;Them&quot; is sometimes used in place of &quot;those&quot; as a demonstrative in both nominative and oblique constructions. Examples are &quot;Them are the pants I want&quot; and &quot;Give me some of them crackers.&quot;    Question(s): What would you say about the usage of this word? Is it correct? Could we use it in daily speech? Could this usage go beyond a specific dialect and be used in other dialects, regions, etc.? Does it really originate from Appalachian English? Why did this usage become popular among other English speakers? Note: I have already seen a similar question:  However, it only says, &quot;ungrammatical,&quot; there. This question is specific to this situation only, and there is more to it. Cascading Drop down in SharePoint Online Can I get the output of a command line program with TeX (using e.g. \read18)? What is the Euler Totient of Zero? Wolfram MathWorld defines the Euler Totient function as follows:  The totient function phi(n), also called Euler's totient function, is defined     as the number of positive integers &lt;=n that are relatively prime to (i.e., do  not contain any factor in common with) n, where 1 is counted as being  relatively prime to all numbers   By this definition would $\phi(0)=0$? If $id:(X,d_1)\to (X,d_2)$ is continuous then what will be $X$? Plot draws list of curves in same color when not using Evaluate Conky Widgets are Opening in their Own Windows I just upgraded to 16.04 and I'm getting all my customization set up again, but it seems that most Conky widgets are opening in their own window, instead of just appearing on the Desktop; although some are working correctly.  For example:  LSD (working properly):    Seamod (not working, opening in own window):    Since it's not affecting every single widget, I assume it could be an issue with the conkyrc with the widgets that aren't working, but this also never happened in 14.04 so I wasn't sure if maybe there was some compatibility issue in 16.04. My Google-fu has failed me in finding a solution.  If anyone can point me in the right direction, it would be much appreciated! :) London Heathrow airport - do I need a transit visa? Help with math symbols in BibTeX I am writing a PhD thesis using LaTeX. Every thing is going fine, but I have problem with the output of the mathematical symbols in the references lists. I copy one example from the Pdf file to make it clear for you. You can see that the fraction remains the same.      [1] Mezzacapo, F. and Cirac, J. I. (2010) Ground-state properties of   the spin-\frac{1}{2} antiferromagnetic Heisenberg model on the   triangular lattice: a variational study based on entangled-plaquette   states. New. J. Phys., 12,   103039.   You can see below the all the packages I use:  \documentclass[12pt,PhD,twoside,a4paper]{GB_muthesis}%[10pt,PhD, singlespace] \usepackage[pdftex]{graphicx} \usepackage[bookmarks=true,colorlinks=true,linkcolor=blue, urlcolor=blue,citecolor=blue]{hyperref} \usepackage[numbers,comma, sort&amp;compress]{natbib} \usepackage{amsmath} \usepackage{amssymb} \usepackage{mathtools} \usepackage{rotating} %\usepackage{GE_manthesis} \usepackage{GB_thesis} \usepackage{bm} \usepackage{fmtcount} \usepackage{setspace} \usepackage{chapterbib} \usepackage{subfigure}% allow subfigures \usepackage{amsfonts} \usepackage{url, enumitem} \usepackage{lscape} \usepackage{notoccite}%This package is for ingnoring the citation in the caption of the figures and tables. \begin{document} What's the name for the relativistic paradox with the train/car travelling over a gap? There is a relativistic paradox I was introduced by a friend in Ithaca (Courtenay Footman). It involves a vehicle travelling over a ravine relativistically, so it's in the general family of ladder paradoxes. There are many ways to phrase it, but here's a simple one.   A three-car train with each car of length $L$ is travelling over a bridge across a ravine. (Assume that the couplings between cars are stiff: this train does not bend.) Unfortunately, some evil genius has precisely removed a length $6L$ of the track. The train however is relativistic, travelling at a speed such that $\gamma \approx 12$.  In the reference frame of the ground, the train should appear to be 1/24th the size of the gap, which suggests that it will fall a little and should crash into the bridge opposite. But in the reference frame of the train, each car of the train is at least twice as long as the gap and aside from the very front wheel and the very back wheel, which need to be supported by rigidity, everything is constantly well-supported. This suggests that the train makes it. Who is right?  I vaguely remember that as an undergraduate knowing only a little relativity, I trusted the train's perspective because it's at rest in that perspective, and Courtenay said that this was ultimately correct after a lot of details got resolved. But I do not remember all of these details such that I could work it out for myself. So I'm looking for some discussion that's a little more well-sourced or authoritative.  What is this paradox called, and what literature has addressed the issue? What is the optimal path between $2$ fixed points around an invisible obstructing wall? Every day you walk from point A to point B, which are $3$ miles apart. There is a $50$% chance each walk that there is an invisible wall somewhere strictly between the two points (never at A or B). The wall extends $1$ mile in each direction perpendicular to the line segment (direct path) between A and B, and its position can be at any random location between the two points. That is, it can be any distance between A and B such as $0.1$ miles away from A, $1.5$ miles away, $2.9$ miles away.... You don't know if the wall is present or where it is until you walk into it.  You must walk around the wall if present as there is no other way to circumvent it.  Assume the wall is negligible thickness (like a force field), all ground is perfectly flat, and the y coordinates at both A and B are $0$ (although I don't think the optimal path will change much if they weren't).  What strategy minimizes the average expected walk distance between A and B?  How do we know for certain this strategy yields the shortest average walking distance?  To get the $100$ bounty points, I would like a convincing argument from you as to why you feel your solution is optimal and cannot be beaten.  For those of you using computer simulation, anything reasonably close to optimal is a candidate for the bounty.   Can anyone beat the optimal solutions submitted so far?  There are still a few days to try.  Even a slight beat (if not due to roundoff error or some other error) would help prove previous solutions are non-optimal.  You can just use the table of $31$ points (x-y coordinates) and compute that path length and then if you can find better then I will accept that answer.  I think by Sunday night I may have to award the bounty otherwise it may get auto-awarded. I have always argued adamantly, as long as the issue has been around, that gift should never be used as a verb. However, someone whose English knowledge I quite respect disagrees.  I’ve done some searching and I haven’t found a consensus; should gifting be shunned?