Unable to update in ubuntu 14.04
How do I remove a malformed line from my sources.list?
What is the white smoke-like fog called? It's not really fog, mist or haze. I used to think that it's mist, but from what I've read here, it turns out that it isn't.  It's the white smoke-like fog that is close to the ground. I've seen it recently above a couple of small ponds (and ground) in a damp forest. It was almost as white as smoke, you can barely see through it, but it is close to the ground, from 20cm to a meter or so.  Since it isn't fog (which is a cloud that you can see, say from a mountaintop, and if it's not mist (which is more like 'rain'), then what is it? Prove: If $a\mid m$ and $b\mid m$ and $\gcd(a,b)=1$ then $ab\mid m$ What are post-installation triggers?  These are executed when upgrading software. Payment from Apple for developer Non-root login on EC2 instance What is the best way to animate the camera path? I'm modeling a car driving along a road(speeds up, slows down, and stops at traffic lights to wait till the lights turn green, etc.) What is the best way to animate the camera path for the following scenario?   The camera starts moving from point A, and it takes 500 frames to get to point B. During this 500 frames, the camera first gradually speeds up, then moves at a constant speed, and finally slows down to a complete stop at point B. The next 50 frames, the camera will stay at point B. From frame 551, it takes another 500 frames to get to point C from point B. The camera experiences the same motion as described in #1 (speeds up, constant speed, slows down, then stop.) Again, the camera will stay at point C for another 50 frames.  Point C to D is a curve path ( added using Shift + A -> add path). I want the camera to move along the path from frame 1101 to frame 1200. The camera should have the same motion as before(speeds up, constant speed, slows down, then stop.)   What is the best way to animate the camera path in this case? Is there any Python scripts available and can be applied to case like this? Thank you all in advance for your replies. I want to create a circuit that can detect audio frequencies and flash RGB LEDs different colors depending on the detected frequency. The frequency range will be from 20 Hz to 12 kHz, after looking at the chart below.   (source: )    So my question is: what circuit design should I choose to make a good frequency detector? I suppose I would need    Preamp for the microphone (is it necessary for the ADC?) Band pass filters (active or passive?) A microcontroller with an onboard ADC that has a sampling rate of at least 24 kHz.   Before I get too excited, are there any circuits out there that already do this? Why (in relatively non-technical terms) are Calabi-Yau manifolds favored for compactified dimensions in string theory? I'm looking to create a virtual printer that passes data to my .NET application. I want to then create an installer that installs both the printer and the .NET application.  It would we really nice to be able to write it all in C#, but I have a feeling that this will require a printer driver to be written is unmanaged code.  Does anyone know of a fairly clean tutorial or example of how to do this? Complex towers: $i^{i^{i^{...}}}$ If $w = z^{z^{z^{...}}}$ converges, we can determine its value by solving $w = z^{w}$, which leads to $w = -W(-\log z))/\log z$.  To be specific here, let's use $u^v = \exp(v \log u)$ for complex $u$ and $v$.  Two questions:   How do we determine analytically if the tower converges?  (I have seen the interval of convergence for real towers.) Both the logarithm and Lambert W functions are multivalued.  How do we know which branch to use?   In particular $i^{i^{i^{...}}}$ numerically seems to converge to one value of $i2W(-i\pi/2)/\pi$.  How do we establish this convergence analytically?  (Yes, I have searched the 'net, including the tetration forum.  I haven't been able to locate the answer to this readily.) How do I set a default host for nginx? I'm trying to figure out how to set a default host for my nginx installation. I found this article in the nginx Wiki:    Unfortunately, this doesn’t work. After restarting I get this:  Restarting nginx: nginx: [emerg] unknown directive "http" in /etc/nginx/sites-enabled/catchall:1 nginx: configuration file /etc/nginx/nginx.conf test failed   After removing the http directive I get this:  Restarting nginx: nginx: [emerg] unknown log format "main" in /etc/nginx/sites-enabled/catchall:7 nginx: configuration file /etc/nginx/nginx.conf test failed   I’m on Ubuntu 10.04.3 where I’m using the official nginx PPA. Version 1.0.9 of nginx is running. I'm using Ubuntu 13.04 on a Lenovo X220.  Why do I have so many .Xauthority.* files in my home directory? I.e  .Xauthority .Xauthority.0JW6UW .Xauthority.2HWRVW .Xauthority.2TA6VW .Xauthority.49F8VW .Xauthority.4E27UW .Xauthority.7CLTVW .Xauthority.8JGGXW .Xauthority.96SAVW .Xauthority.AOUFVW .Xauthority.ASDOVW .Xauthority.CGVJXW .Xauthority.E0ZSVW .Xauthority.E5VZWW .Xauthority.FE64UW .Xauthority.FIHDWW .Xauthority.HL45VW .Xauthority.HYCCVW .Xauthority.ILUEWW .Xauthority.JXJHVW .Xauthority.K1QJXW .Xauthority.KXSOVW .Xauthority.LEKEVW .Xauthority.M48WVW .Xauthority.M6QTVW .Xauthority.MW6NWW .Xauthority.N57TWW .Xauthority.O5HAWW .Xauthority.OIC5VW .Xauthority.P2RPVW .Xauthority.Q0FRVW .Xauthority.QW01WW .Xauthority.RDW5WW .Xauthority.T0TLWW .Xauthority.TSO4WW .Xauthority.U6R9VW .Xauthority.V3KAWW .Xauthority.W8Z1WW .Xauthority.XDLGVW .Xauthority.XOOHWW.Xauthority.XUICVW  They are all zero bytes except the first, with timestamps all over the place.  What are these, and are they safe to delete? Can any one explain me what is the use of derivatives in real life. When and where we use derivative, i know it can be used to find rate of change but why?. My logic was in  real life most of the things we do are not linear functions and derivatives helps to make a real life functions into linear.  eg converting parabola into a linear function $x^{2}\rightarrow 2x$  but then i find this; derivation of $\sin{x}\rightarrow \cos{x}$  why we cant use $\sin{x}$ itself to solve the equation. whats the purpose of using its derivative $\cos{x}$. Please forgive me if i have asked a stupid questions, i want to improve my fundamentals in calculus. Beamer Bibliography Icon I want to list my references in a beamer presentation using thebibliography environment, with the nice little    book icon (\beamertemplatebookbibitems) and  article icon (\beamertemplatearticlebibitems)   in front of each source.  Is there an icon for websites too? something like \beamertemplatewebsitebibitems? If not, is there a way to implement this easily ? Let $(M,d)$ be a metric space, and $A\subset M$. By definition, $A$ is said to be compact if every open cover of $A$ contains a finite subcover.  What is wrong with saying that, in $\mathbb{R}$, if $I=(0,1)$, we can choose $G=\{(0,\frac{3}{4}), (\frac{1}{4}, 1)\}$, which satisfies $I \subset \bigcup_{U\in G} U$, but we can't extract a finite subcover, so $I$ is not compact. Is $G$ a finite subcover of $G$, so it is not a valid cover for proving this? I would take $\cup_{n\in\mathbb{N}} (\frac{1}{n},1)$ in order to prove this, can we conclude that every open cover is necessarily a infinite union of open sets $\neq \emptyset$? I intend to use fsck for checking my Linux partition of the main disk, because its file system is suspicious of being not unmounted cleanly by shutting down the system. I have searched in my environment variables: none of them except of PATH should control the fsck program. But the program apparently needs to be used during a boot: :~$ fsck -V fsck from util-linux 2.20.1 Checking all file systems. [/sbin/fsck.ext4 (1) -- /] fsck.ext4 /dev/sda6  e2fsck 1.42 (29-Nov-2011) /dev/sda6 is mounted. WARNING!!!  The filesystem is mounted.   If you continue you WILL cause SEVERE filesystem damage. Do you really want to continue? no check aborted.  (There is no /forcefsck file in my root according to  . My etc/fstab file contains    # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # #                 proc            /proc           proc    nodev,noexec,nosuid 0       0 # / was on /dev/sda6 during installation UUID=1ac55d8d-c112-4bc7-9e79-921d196f9f79 /               ext4    errors=remount-ro 0       1 # swap was on /dev/sda7 during installation UUID=54f7e314-50e2-419b-a45d-47c3058ecc00 none            swap    sw              0       0 /dev/fd0        /media/floppy0  auto    rw,user,noauto,exec,utf8 0       0   ). According to an answer to  I have tried tune2fs hoping that I'll get the present value of the max_mounts_count parameter to be able to set it to 1 for checking the partition during the next boot. But after sudo rm /var/lib/update-notifier/fsck-at-reboot and a restart I have only got a response  :~$ tune2fs -l /dev/sda6 tune2fs 1.42 (29-Nov-2011) tune2fs: Permission denied while trying to open /dev/sda6 Couldn't find valid filesystem superblock. Can I use sudo tune2fs -l /dev/sda6 safely? Thanks. If $I_n=\int _0^{\pi }\sin^{2n}\theta \:d\theta $, show that $I_n=\frac{\left(2n-1\right)}{2n}I_{n-1}$, and hence $I_n=\frac{\left(2n\right)!}{\left(2^nn!\right)2}\pi $  Hence calculate $\int _0^{\pi }\:\sin^4t\cos^6t\:dt$  I knew how to prove that $I_n=\frac{\left(2n-1\right)}{2n}I_{n-1}$, but I am not very good at English, what does it mean Hence $I_n=\frac{\left(2n\right)!}{\left(2^nn!\right)2}\pi $ do we need to prove this part as well or is it just a hint to use? and for the other calculation to find $\int _0^{\pi }\:\sin^4t\cos^6t\:dt$ is there something in the first part that I can do to help me solve this question because otherwise it becomes very long and it's part of the question. Following the guidelines suggested in , I am going to post a proposed proof as an answer to the theorem below. I believe the proof works, but would appreciate any needed corrections.  Theorem If a series $\sum_{n=1}^{\infty}a_n$ of real numbers converges then $\lim_{n \to \infty}a_n = 0$ Is it always better to use 'DbContext' instead of 'ObjectContext'? I am simply adding user in 'Monitored Users' in Debug Logs. But User is not getting added.