Understanding how EOF and Ctrl + D work
Canonical vs. non-canonical terminal input
Tracking disk I/O by application in Windows? What are the biggest pros and cons of  vs ? Vectors and Norms If $a$ and $b$ are vectors such that $\|a\| = 4$, $\|{b}\| = 5$, and $\|{a} + {b}\| = 7$, then find $\|2 {a} - 3 {b}\|$.  I couldn't figure out how to start off this problem. I attempted to use $$\cos \theta = \frac{a\cdot b}{\|a\|\cdot \|b\|}$$ But I still don't know what to do. Could someone nudge me in the right direction?  Thank you! Materials for learning TikZ I feel intimidated in learning TikZ. I was wondering if there are some nice materials (or just your replies) at different level:   for providing big picture, which is important to beginners to not lose direction during learning. for comprehensive reference.   Examples are important, but only examples are not always clear for understanding the big picture and organization. I am travelling to Budapest and therefore have a Schengen Visa. I hold an Indian passport and a valid US visa. I'm travelling from Chicago-Heathrow-Budapest and returning by Budapest-Dublin-Chicago.  Would I need a transit visa for UK/Ireland?  UPDATE  Hoping this will help someone someday.   I was not allowed to board my return flight (BUD-DUB-ORD) because I do not hold an overnight Irish Transit Visa. They said I could have transited happily if the connecting flight was in the same day, but because I would have to originally land at 10 PM and catch the connecting flight next morning at 10 AM, I needed a transit visa. Well, I thought it was BS, but couldn't help comply with the rules. I booked another last minute ticket and flew via Warsaw via LOT. How could it possible to factorise $x^8-1$ in product of irreducibles in the rings $(\mathbb{Z}/2\mathbb{Z})[x]$ and $(\mathbb{Z}/3\mathbb{Z})[x]$? How could it possible to factorize $x^8-1$ in product of irreducibles in the rings $(\mathbb{Z}/2\mathbb{Z})[x]$ and $(\mathbb{Z}/3\mathbb{Z})[x]$?  I'm having a hard time starting the problem. Could anyone help me at this point? Excel How to make Text Qualifier editable or add a new entry in the existing list? In another  regarding a difference between short on and short of, the  says the following:     ... But this is not always the case. A person can be short on/of money,   but lacking a specific amount, someone can only be €10 short or short   €10. This construction never uses a preposition.   but is that really true? I can see sentences like "I am short of 10 dollars" quite often. Is there a documentclass that produces 'endless' pages? Does anybody know of a documentclass that produces a page that has a fixed width and a variable length, depending on the actual content that needs to fit on the sheet? I'm trying to get something like a kind of scroll if possible. MySQL shutting down without warning, out of memory? I've seen a couple other questions with this error message but it seemed that the host and ip in question were ones the OP knew. These two are unrelated to my server.  Where and why is postfix generating this error?     Jul 24 17:42:14 email postfix/smtpd[32277]: warning: hostname kimtake.respectedopinion.com does not resolve to address 62.210.28.114   Jul 24 17:42:14 email postfix/smtpd[32277]: connect from unknown[62.210.28.114]   Jul 24 17:42:14 email postfix/smtpd[32277]: disconnect from unknown[62.210.28.114] Is there a phrase that means sleeping with someone without sex? On my headless NAS I have sdf1 (a flash-card) mounted as / while /home is mounted from lv00 (an LVM volume backed by a software RAID). To be able to access the machine when the RAID fails, I have a copy of my ssh public key, etc. in /home/foo/.ssh on the file-system from sdf1. To update the files that are hidden by the mounted /home I normally remount lv00 in /mnt/home, do what I have to do, and then move lv00 back in place. Is there a way to achieve this without unmounting /home? How could Luke hide from Vader during the duel on Death Star II? In Return of the Jedi, Vader throws his lightsaber at Luke causing the catwalk come crashing down. Luke uses this in his advantage and hides from him under the throne room platform. Unable to locate his son, Vader tried to lure Luke out of hiding.  But how could Luke conceal himself from Vader in the first place? Did he use a Force power of some kind to blur Vader's sensors? I mean, the underneath of the platform was pretty much an open space with very little possibilities for hiding. The only places I see in the movie are the openings on the both sides of the floor (pointed by the yellow arrows):    The background of a close-up to Luke doesn't give much of a clue (although there is a round shape which could be the bottom of a window frame):    But as Luke reveals himself, he appears to be beneath of the staircase to the dais, right in the middle of it:    There's no way he could have hidden there all the time, because just a couple of seconds before, Vader walked towards and stared at the very same spot:    My first ideas were that Luke used the Force to make himself invisible, or to teleport him to the position. But after taking a look at one of the cross sections of the Emperor's throne room, I assume Luke could have slid almost straight under the floor of the lower level (yellow arrow) and then later  back to the staircase (although we don't see it in the movie, and I'm not sure if Luke knew the ability):    Does someone know better? Defer Parsing of Scripts this is my first time to try this "Defer Parsing" thing, and I don't really have an idea how to do it.    Using PageSpeed tool, I found out that one of the reason why my page is loading too slow (currently 92/100) are the scripts. And the PageSpeed suggested that I need to Defer Parsing all those scripts.  Is there anyone that can help me with this. Thanks. How do I migrate an SVN repository with history to a new Git repository? Are there any series whose convergence is unknown? Are there any infinite series about which we don't know whether it converges or not? Or are the convergence tests exhaustive, so that in the hands of a competent mathematician any series will eventually be shown to converge or diverge? EDIT: People were kind enough to point out that without imposing restrictions on the terms it's trivial to find such &quot;open problem&quot; sequences. So, to clarify, what I had in mind were sequences whose terms are composed of &quot;simple&quot; functions, the kind you would find in an introductory calculus text: exponential, factorial, etc. Access Java / Servlet / JSP / JSTL / EL variables in JavaScript 'A / One / At least one student entered the room.' Are these the same? (truth-conditionally) I just wonder if the two following sentences are truth-conditionally the same. Sentence 1 essentially means there existed a student who entered the room, and this situation includes two, three or more students entering the room. Hence, I believe these two sentences are truth-conditionally the same. Are they?        A student entered the room.   At least one student entered the room.      How about        One student entered the room      I gather this is different, as sentence 3 only means one student, not more and not fewer?  Any and all insights would be welcome. When installing user applications, where do "best practices" suggest they be located? Occasionally I install applications manually, rather than using apt or another package manager.   What location (/usr/, /usr/local/, /opt/, /home/, etc.) is suggested by "best practices" for the installation of user applications?