Could we fix the dates in the example question in SO tour? The new top nav-bar helped me navigate to the fancy  again, but the example question caught my eye.  The example shows that the question was answered a year before it was asked.    Minor issue, I know.  But could we fix this, please?
The real fastest gun in the west Are the questions in the about page taken from real posts? If not, who designs them?  Particularly, why does this specific answer have a date from before the question was asked?
Python Implementation of Track-to/aim constraint On , this is my tag blacklist:        Note well that I have them set to hidden, because I would prefer not to see questions on this topic. Bridge players, don't take offence &mdash; I don't have problem with the game itself. I don't understand the game's mechanics, though, so I find questions about it incomprehensible, and I'd rather stick to just seeing questions I can understand.  I still see [bridge] questions galore on the Android app though. Could it be updated to pay attention to whether I have certain tags ignored and set to be hidden? I drew a parallelepiped that is spanned by three vectors, and we know the volume is given by the absolute value of the determinant of the matrix - with the three vectors arranged in rows (or columns, since $detA = detA^T$).  How can I draw the tetrahedron from this parallelepiped to convince myself it is indeed 1/6th of the volume, i.e., 1/6 * |detA|?  Thanks, Non-finite clause complementation of complex transitive verbs This question has been bothering me for a while. It came up when I was reading Chapter 16 of "A Comprehensive Grammar of the English Language."   How to explain the grammatical structure of the following four sentences?    "We knew him to be a spy." "I saw her leave the room." "I heard someone shouting." "I got the watch repaired."    What category do the four non-finite clauses in boldface fall into? They do not seem to fall into any of relative, nominal, comparative and adverbial clauses. General identity for a double summation theorem I've been reading a research paper, and I'm interested in generalizing a certain theorem but I can't seem to understand how the following results are derived:  $$\sum_{i=1}^{n}\sum_{j\neq i}^n \frac{1}{z_i-z_j}=0$$  $$\sum_{i=1}^{n}\sum_{j\neq i}^n \frac{z_i}{z_i-z_j}=\frac{1}{2}n(n-1)$$ $$\sum_{i=1}^{n}\sum_{j\neq i}^n \frac{z_i^2}{z_i-z_j}=(n-1)\sum_{i=1}^n z_i$$ $$\sum_{i=1}^{n}\sum_{j\neq i}^n \frac{z_i^3}{z_i-z_j}=(n-1)\sum_{i=1}^n z_i^2 + \sum_{i&lt;j}^n z_i z_j$$ How do I handle elastic contacts in a simulation with friction I'm trying to simulate a wheel as it hits the ground.  Problem 1  Suppose a disc is dropped from a height. It has initial velocity of $-x,-y$ caused by throwing and gravity. It has no initial angular velocity. When it hits the ground it should have some rotation resulting from the collision.   How to calculate force that caused torque for that rotation?   Problem 2  The same disc is dropped from height. It doesn't have velocity on the side direction. It already spinning fast. When it hits the ground the spinning should cause some translation.   How to calculate force that caused this linear acceleration? Some rotation must be lost in the collision, how to calculate that?   To simplify assume static $friction = 1$ and $g = -10$. When writing my custom function I need to manually append node name to a taxonomy term link. To get the taxonomy term part done I use:    $link_uri = taxonomy_term_uri($term);   $path_alias = drupal_get_path_alias($link_uri['path']);   This works ok, now - I want to append node name ("/" . $node_name), but instead of raw string, I want the Pathauto transliterated output, as set in the URL alias configuration, for that node context.  What function should I use to mimic that output? I looked at hook_pathauto_alias_alter(&amp;$alias, array $context) but I'm not sure that's what I need. How to show that for all k, $k! \ge (k/2)^{k/2}$ migrating / merging iphone contacts I have an iPhone 6 (with proper iTunes backup) where all of my contacts where, but I bought a new iPhone 7 and had to initialize it as new iPhone, due to several time-related constraints, so now I have a few but new contacts on my new phone, but none of the older ones, but would be the best practice oriented, for just recovering the old contacts from the iTunes backups?  PS: I still have the old iPhone 6, so it could be used as "temporary storage" if needed. How do I handle null or optional DLL struct parameters How do you use plural or singular form of an adjective? So I was taught that you should almost always use singular form of an adjective instead of plural form. But recently, I've seen people using plural form and it sounds quite weird and I don't know if it is correct.  For example,   "Salary tax" instead of "Salaries tax" "Office supplies" instead of "Offices supplies" "Product demo" instead of "Product demo"   In the above cases, the word "Salary" is used as an adjective to describe the type of "tax", so it will be in singular form. But I saw people using salaries tax and not sure if it is grammatical.  So my question is if there are any general rules on how to use the singular/plural form of an adjective? I have scripts calling other script files but I need to get the filepath of the file that is currently running within the process.   For example, let's say I have three files. Using :   script_1.py calls script_2.py.  In turn, script_2.py calls script_3.py.    How can I get the file name and path of script_3.py, from code within script_3.py, without having to pass that information as arguments from script_2.py?  (Executing os.getcwd() returns the original starting script's filepath not the current file's.) How to sample from a discrete distribution? Assume I have a distribution governing the possible outcome from a single random variable X.  This is something like [0.1, 0.4, 0.2, 0.3] for X being a value of either 1, 2, 3, 4.  Is it possible to sample from this distribution, i.e. generate pseudo random numbers upon each of the possible outcomes given the probability of that outcome. So if I wanted to know what the probability of getting a 2 is, the sampling operation may return 0.34 or something like that.  The reason I ask is that I'm trying to implement an action selection policy for a reinforcement learning method based on a research paper. From what I gather from the paper, the author is able to sample the distribution by "mapping the uniform distribution U[0,1] through cumulative probability density functions obtained by adaptive numerical integration". From this he then samples the transition probabilities for each trial...  I would be grateful for any info on this...  Thanks in advance A white number inside a black circle. How to make a white number inside a black circle (the picture below)? I want to change numbers inside the black circle, of course.  I use Share LaTeX. I have read some articles here but anyone are not what I would like to get. I would like to get this  (the picture below) - the sixth answer.   Thanks for help. How can I put the computer to sleep from Command Prompt/Run menu? I know that almost everything on Windows, like opening any sort of application, can be done from the command prompt or from the Run menu.  How can I put my computer to sleep or shut it down? What is the command for that? After swapping the positions of the hour and the minute hand, when will a clock still give a valid time? At 12 o'clock, the hour hand and minute hand of the clock can be swapped, and the clock still gives the same time, but at 6 o'clock, it can not be swapped. So in what cases when we swap the hour and the minute hand position does a clock still give a valid time? Proof that every finite dimensional normed vector space is complete Can you read my proof and tell me if it's correct? Thanks.  Let $V$ be a vector space over a complete topological field say $\mathbb R$ (or $\mathbb C$) with $\dim(V) = n$, base $e_i$ and norm $\|\cdot\|$. Let $v_k$ be a Cauchy sequence w.r.t. $\|\cdot\|$. Since any two norms on a finite dimensional space are equivalent, $\|\cdot\|$ is equivalent to the $l^1$-norm $\|\cdot\|_1$ which means that for some constant $C$, $\varepsilon &gt; 0$, $k,j$ large enough, $$ \varepsilon &gt; \|v_j - v_k\| \geq C \|v_j - v_k\|_1 e_i= C \sum_{i=1}^n |v_{ji} - v_{ki}| \geq |v_{ji} - v_{ki}|$$ for each $1 \leq i \leq n$. Hence $v_{ki}$ is a Cauchy sequence in $\mathbb R$ (or $\mathbb C$) for each $i$. $\mathbb R$ (or $\mathbb C$) is complete hence $v_i = \lim_{k \to \infty} v_{ki} $ is in $\mathbb R$ (or $\Bbb C$) for each $i$. Let $v = (v_1, \dots , v_n) = \sum_i v_i e_i$. Then $v$ is in $V$ and $\|v_k - v\| \to 0$:  Let $\varepsilon &gt; 0$. Then $$ \|v_k - v\| \leq C \|v_k - v\|_1 = C \sum_{i=1}^n |v_{ki} - v_i| \leq C^{'}n \varepsilon$$  for $k$ large enough. Expected time to roll all 1 through 6 on a die What is the average number of times it would it take to roll a fair 6-sided die and get all numbers on the die?  The order in which the numbers appear does not matter.  I had this questions explained to me by a professor (not math professor), but it was not clear in the explanation.  We were given the answer $(1-(\frac56)^n)^6 = .5$ or $n = 12.152$  Can someone please explain this to me, possibly with a link to a general topic? If you know what a number mod two different primes is (3 and 2) in this case, how can you tell what the mod is of the two products? Let $ D = 2^\mathbb{N} $, i.e., D is the set of all sets of natural numbers.   What's the meaning of this definition? Intuitively, I would suggest that $ D = \{1,2,4,...\} $ but the explanation "set of all sets" leads me to the guess that this is wrong.