question regrading double cone
The double cone is not a surface.
If every polynomial of degree 2 is reducible then $K$ is algebraically closed? I'm using C# on Framework 3.5.  I'm looking to quickly sort a Generic List&lt;T&gt;.  For the sake of this example, let's say I have a List of a Person type with a property of lastname.  How would I sort this List using a lambda expression?  List&lt;Person&gt; people = PopulateList(); people.OrderBy(???? =&gt; ?????) How to control fan speed? Efficiency of a heat pump water heater during the winter In my understanding, heat pump water heaters pump energy from the room around the water tank into the water.  Clearly, this must be energy efficient in the summer time, especially if I am using AC anyway. The heat pump water heater may actually cool the house a bit.  However, in the winter time the savings are not so obvious. If I am using a heater to heat the home, including the water tank room, then I don't see how there can be any savings. Instead of generating heat using a coil in the water, I generate heat in another area of the house which gets pumped into the water. A joule is a joule and I need to get it from somewhere. It seems to me that if I am actively heating the house, and lets assume everything is electric, then a heat pump water heater cannot be more efficient than a traditional one.  Am I missing something in the winter case? Showing there is no ring whose additive group is isomorphic to $\mathbb{Q}/\mathbb{Z}$ Show that there is no commutative ring with the identity whose additive group is isomorphic to $\mathbb{Q}/\mathbb{Z}$. Why commutator subgroup is normal to G? If $G$ is a group and $G'$ is generated by $\{xyx^{-1}y^{-1}|x,y\in G\}$, then $G'\trianglelefteq G$ and  $G/G'$ is Abelian.  At first, I thought this is easy because I thought $g[x,y]g^{-1}=[gxg^{-1},gyg^{-1}]$. But it was a mistake. I could not prove that it is also subgroup of G and $G/G'$ is abelian. I need help. What are some scenarios where FTL information transfer would violate causality? I've always heard people saying, "Faster than light information transfer can't happen because it would violate causality!  Effects can precede their causes!"  However, I'm trying to think of a situation where this would happen.  I'm sure it has something to do with relativity or something like that.  I sort of understand that people going faster perceive time slower.  Can someone help illuminate this for me by showing a scenario where causality is clearly violated due to FTL information transfer? An unclear sentence in the book "Griffiths, Harris-Principles of algebraic geometry" how implement the jqueryUI in visualforce Ill implement the some UI but its not working in the visualpage , can u know how implement jquery ui in viusalpage ,  Kindly tell the procedure ,     Im using this url its not working ,,,,, Why do gaps appear in my mesh when I animate it? As I attempt to complete a "Walk cycle" with my model, the mesh at the pants line separates from the skin as the model moves or as I rotate the controls. This happens in many places on my model and it reveals the model interior. It is a one piece mesh, though, so I don't understand why this happens. Is this caused by weight painting problems? How can I fix this? Vi on Linux: show ^M line endings for DOS-format files On Solaris, if you open a file in vi that has Windows line endings, this shows up as ^M at the end of every line.  On Linux, vi is cleverer and understands the Windows file format, and does not display ^M.  Is there a setting to make Linux vi behave the same as Solaris in this respect?  A common problem for us is copying a shell script off a (Windows) dev box and forgetting to dos2unix it, and then being confused when it doesn't work properly. On Solaris the problem is obvious as soon as you vi the file, but not on Linux.  Thanks. I am wondering if we should use  or  for buttons and headings in websites and web/mobile apps? Title Case: Manage my Account Delete my Account  Sentence case: Manage my account Delete my account  In  I found the recommendation 'choose your style and be consistent'. This is it? Aren't there any other (additional) recommendations or sources. Like for specific use cases or apps where the one style would be preferred over the other? Edit: The question refers primarily to English, but differences in other languages are also good to know. Calendar date to yyyy-MM-dd format in java Are there rules for using manacles in combat? I can't quite find in the PHB or DMG how to slap manacles onto someone during combat. PHB 152 describes how to break out of mundane manacles, while DMG 165 shows how Dimensional Shackles work (they are essentially magic manacles -- use 1 action to bind an Incapacitated target).  Is there an official rule on how to use manacles in combat, or do we have to use house rules? How could I get the terminal to be launched once I have logged in, so that typing commands is much simpler? I vaguely remember a SciFi novel from my younger days, where scientists discover "alternative" forms of power beside electromagnetism.  I do not remember the specific forms, but it was something along the lines of "electrogravity", "magnetogravity" etc. -- you get the idea. If I remember correctly, the effects of these power forms were basically psionic / magic in nature.  Unfortunately I remember very little of the actual plot, and couldn't put it into words with any coherency. Some treachery from within the group of scientists, perhaps some involvement of aliens? I cannot really remember. I just remember I enjoyed the story very much, and would like to re-read it.  The title could be "The fifth column" or similar -- then again I might be confusing two seperate novels.  I know that's not much, sorry. Anyone remembers this? Advanced search in Google Contacts Is there any way to do perform advanced searches in Google Contacts?  For example, wild card operators, AND operator, OR operator etc?  I want to search anywhere in a name, not just the beginning of a name. (i.e if I write 'ac' it should display Jack as well) Prediction interval for binomial random variable What is the formula (approximate or exact) for a prediction interval for a Binomial random variable?  Assume $Y \sim \mathsf{Binom}(n, p)$, and we observe $y$ (drawn from $Y$). The $n$ is known.  Our goal is to obtain a 95% prediction interval for a new draw from $Y$.   The point estimate is $n\hat{p}$, where $\hat{p}=\frac{y}{n}$. A confidence interval for $\hat{p}$ is straightforward, but I cannot find a formula for a prediction interval for $Y$. If we knew $p$ (rather than $\hat{p}$), then a 95% prediction interval just involves finding the quantiles of a binomial. Is there something obvious I'm overlooking? How can I get file extensions with JavaScript? See code:   var file1 = "50.xsl"; var file2 = "30.doc"; getFileExtension(file1); //returns xsl getFileExtension(file2); //returns doc  function getFileExtension(filename) {     /*TODO*/ } Using only the delta definition of a limit, how can we prove that the sequence $\{a_n\}$, where $a_n = \sin n$, as $n$ tends to infinity does not have a limit?  Thanks!