Always wanted a clear explanation as to why these animals had double letters at the beginning of the spelling. What’s up with that?
Usually, when we see two letters put together it is to define the pronunciation or to differentiate synonyms or just its foreign origins. But some words don't seem to have any reason to double up.     Why does vacuum have two of the letter U?  Why does aardvark have two of the letter A?  Why does llama have two of the letter L?
There's a book I borrowed from my grade 8 teacher's lending shelf (in Ontario, Canada) that I've been trying to identify for years. The main character was a man in a futuristic setting who... I think... had the secret to an improved version of the lifespan-extension serum everyone used. If I remember correctly, the flawed version caused people's skin to turn clear over the course of their extended lives. I think he was revived from some sort of stasis, but I can't be sure of that. I just vaguely remember a &quot;stranger in a strange land&quot; sort of cultural disconnect, him being cared for in some kind of hospital-like setting, and a sense that maybe the formula they want from him was invented by a now-dead family member of his. The most distinctive detail I remember was the love interest, a cloned nurse named &quot;Eliza Tertia&quot; who he encourages to break out of her role. (All the cloned nurses were named Eliza, and I remember &quot;Eliza Duodecima&quot; being the name of another one who is briefly seen.) I also remember the secret eventually being gotten out of him, only for it to be discovered that it's flawed, in that, while it does replenish the compounds that go missing in extended old age, it doesn't moderate their production. I don't remember if it was long enough to be a novel or if it was just a novella. My vague memories of the cover design and material suggest it was a 1970s printing or earlier, which would also fit with what I remember of the story's atmosphere. Set multicolumn width to default table width Verify is tautology by using logical equivalence Verify is tautology by using logical equivalence:  $$((p ∨ q) ∧ (p → r) ∧ (∼ r)) → q$$  by showing what laws are using, step by step explanation needed.  Logical equivalence: de morgan's laws, commutativity, associativity, double negative, distribution, idempotent, absorption, identity, universal bound, negation  Rules of inference: modus ponens, modus tollens, generalisation, specialisation, conjunction, ellimination, transivity, proof by division into cases, contradiction  What I got so far:  I need to prove   $$((p ∨ q) ∧ (p → r) ∧ (∼ r)) → q ≡ \text{tautology}$$ Since $p → r$ same as $∼ p ∨ r$: $$((p ∨ q) ∧ (p → r) ∧ (∼ r)) → q ≡ ((p ∨ q) ∧ (∼ p ∨ r ) ∧ (∼ r)) → q$$  I am stuck here This comes from a brain teaser but I'm not sure I can solve it:     You are in a rowing boat on a lake. A large heavy rock is also in the boat. You heave the rock overboard. It sinks to the bottom of the lake. What happens to the water level in the lake? Does it rise, fall or stay the same?   I'd say that the water level drops, because when you drop the stone in the lake, the water level rises according to the volume of the stone, BUT the water level decreases by a volume of water weighting the stone's weight, when you take it off the boat.  Is that correct? How can native English speakers read an unknown word correctly? I have learned English for many years, and from the first day I began to learn it I know the dictionary is necessary for the study.  One of the important aspects is that English words, unlike German and Spanish, usually can not be read correctly without phonetics.  But recently, I talked with some native speakers and they told me they can read any word directly and rightly even though they never learned it before.  I just want to know how they can do that -- there is no ordinarily acceptable method to read an English word? Is Linux Virtual Server old, or is it standing still? Based on this question: , LVS may be the right solution for my problem.   But when I went to its homepage , I found that LVS has been updated since Nov, 2008. The world's moving fast, and I don't know if LVS was obsolete or not.  Is LVS standing still, or there're some better solutions to replace it?  Thank you so much. Average length of the longest segment This post is related to a previous SE post  concerning average length of a smallest segment.  A rope of 1m is divided into three pieces by two random points. Find the average length of the largest segment. My answer is 11/18.  Here is how I do it:  Here we have two independent random variables $X,Y$, both uniform on $[0,1]$. Let  $A=\min (X,Y), B=\max (X,Y)$ and $C=\max (A, 1-B, B-A)$. First we want to find the probability density function $f_C(a)$ of $C$. Let $F_C(a)$ be the cumulative distribution function. Then $$ F_C(a) = P(C\le a)=P(A\le a, 1-B\le a, B-A\le a).$$  By rewriting this probability as area in the unit square, I get $$F_C(a)=\left\{\begin{array}{ll} (3a-1)^2 &amp; \frac{1}{3}\le a\le \frac{1}{2}\\ 1-3(1-a)^2 &amp; \frac{1}{2}\le a\le 1\end{array}\right.$$ from which it follows that  $$f_C(a)=\left\{\begin{array}{ll} 6(3a-1) &amp; \frac{1}{3}\le a\le \frac{1}{2}\\ 6(1-a) &amp; \frac{1}{2}\le a\le 1\end{array}\right.$$ Therefore the expected value of $C$ is $$\int_{1/3} ^{1/2}6a(3a-1) da+\int_{1/2} ^{1}6a(1-a) da= \frac{11}{18}.$$  My questions are:  (A) Is there a "clever" way to figure out this number 11/18?  (B) What is the answer if the rope is divided into $n&gt;3$ segments? I updated the chrome to version 61, and the auto-scroll stopped working, it is necessary to scroll down the page manually. The problem does not occur in the previous version or in firefox.  Also, the reply icon no longer working when the message replied to is not in the current chat page. (Middle click still works and opens the link in new tab.) How would one go about proving that the rationals are not the countable intersection of open sets? I'm trying to prove that the rationals are not the countable intersection of open sets, but I still can't understand why   $$\bigcap_{n \in \mathbf{N}} \left\{\left(q - \frac 1n, q + \frac 1n\right) : q \in \mathbf{Q}\right\}$$   isn't a counter-example. Any ideas? Thanks! Number of possible permutations of n1 1's, n2 2's, n3 3's, n4 4's such that no two adjacent elements are same? Given $n_1 $ number of  $1 $'s,  $n_2 $ number of  $2 $'s,  $n_3 $ number of  $3 $'s,  $n_4 $ number of  $4 $'s.  form a sequence using all these numbers such that two adjacent numbers should not be same.  I have tries lot of things but nothing worked.  can somebody tell me how to solve this problem? I am visiting a friend in Switzerland for ten days. I have already got visitor's visa for the same on my Indian passport. Particulars mentioned on my visa are:  1. 'Etats Schengen' , 2. Single entry 3. Dates of visit. &amp; 4. Type of visa : C.  I understand that having already got ‘Etats Schengen' visa, I can travel to all Schengen countries.  I am also planning to visit Paris for a day during my stay in Switzerland. However, I never mentioned this in my visa application. I am planning to take a train from Geneva to Paris and book a hotel in Paris for one night. Can I possibly plan my Paris trip this way as I have Schengen visa, or I am not allowed to travel out of Switzerland as I never mentioned this in my visa application?   Also what does Single entry on my Schengen visa means: does it mean that I can enter and leave Switzerland only once or it means that I can enter and leave the Schengen region only once. I want to prove the  over a field are prime ideals. To be concrete:      For simplicity, let $I=(x_{11}x_{22}-x_{12}x_{21},x_{11}x_{23}-x_{13}x_{21},x_{12}x_{23}-x_{13}x_{22})$ be an ideal of the polynomial ring $k[x_{11},\ldots,x_{23}]$. I have no idea how to prove that $I$ is a radical ideal (i.e. $I=\sqrt{I}$). Could anyone give some hints?   Generally, let $K$ be an algebraically closed field, then $\{A\mid\mathrm{Rank}(A)\leq r\}\subseteq K^{m\times n}$ is an irreducible algebraic set (I first saw this result from ). And I tried to prove this by myself, then I have proved it (when I see the "Segre embedding").      But I have no idea how to show that the "determinantal ideals" are radical ideals (I hope this is true). BTW, is the statement that the determinantal ideals over a field are prime ideals true ?   Thanks. Creating volumetric lighting (crepuscular rays) in Cycles (a.k.a. "god rays" and many other names) can be created in Blender Internal by checking the Halo checkbox in the lamp properties box.  How can I create a similar effect using Cycles? In Obi-Wan's Order 66 warning transmission why didn't he tell the surviving Jedi about the Sith, including Palpatine's true identity? If you've seen the premiere episode of Rebels, you will have seen Obi-Wan's warning message that he broadcast to Jedi throughout the galaxy in RotS. In this message he speaks cryptically &amp; warns of a "dark shadow" falling &amp; to avoid the temple &amp; await a "new hope".   Wouldn't it have been useful to inform the Jedi that their mortal enemy the Sith had returned? And specifically that Palpatine himself was a Sith? You'd assume that the majority of the Jedi who were not in the loop of the Council would be unaware of the existence of the Sith. Yoda mentions a few times that they should keep it under wraps. I think now would've been the time to reveal the truth. The more info the surviving Jedi have the better. Who knows if the likes of Kanan knows anything about the Sith's return! I find Obi-Wan's omission of this information bizarre. "Who wants ice-cream?" — Should I say "(not) I" or "(not) me"? With the enthusiastic question of "Who wants ice-cream?", what is the more correct response?         (Not) I.   (Not) me.      Neither response is a sentence. The first response of "(not) I" sounds stuffy, like it should be followed with an indignant sniff. The second sounds like American idiom and acceptable for casual speech.    What do you say? What does this notation mean? $f(x) \equiv A$? If $\lim_{x\rightarrow\infty}f(x) = A$, prove that $f(x)\equiv A$.  Any help would be appreciated! I just don't even understand the question. I'm self studying J. Lee's Introduction to Topological Manifolds, and after doing all other exercises on chapter 2, I can't seem to come with the proper counterexamples for this one.      For each of the following properties, give an example consisting of two subsets $X, Y \subset \mathbb{R}^2 $, both considered as topological spaces with their Euclidean topologies, together with a map $f: X \rightarrow Y$ that has the indicated property.         Open but not closed/continuous   Closed but not open/continuous    Continuous but not open/closed         etc... (all cases)   I think the reason for my difficulty is a lack of geometric intuition of what open, closed and continuous maps look like as deformations of shapes in $\mathbb{R}^2$ (I can construct counterexamples from artificial made up spaces).   I tried squashing balls and 'pumping space' into lines, as well as joining strips in annulus shapes, but all the examples I seem to come up with are either too well behaved (i.e. all 3) or too misbehaved.   Instead of a case by case answered I would prefer a couple worked out cases and some intuition on how to visualise open / closed maps in this context. Is Stack Exchange / Stack Overflow available for private or internal use? Is the Stack Exchange engine that powers Stack Overflow available to download or install internally for an enterprise or company?  I think Stack Exchange's engine is very great and could be very cool to use for internal enterprise patterns and practices, like the engine of Wikipedia. Combinatorial proof of $\sum^{n}_{i=1}\binom{n}{i}i=n2^{n-1}$. I have a large set of data points of the form (mean, stdev). I wish to reduce this to a single (better) mean, and a (hopefully) smaller standard deviation.  Clearly I could simply compute $\frac{\sum data_{mean}}{N}$, however this does not take in to account the fact that some of the data points are significantly more accurate than others.  To put it simply, I wish to preform a weighted average of these data points, but do not know what the weighting function should be in terms of the standard deviation.