How do I Plot tangent line equation on the given point on the same axes?
Finding the 1st three derivatives of a function and plotting all four curves
Do citizens migrate closer to their workplace within the town? By using the Path tool (F2, 7) I have found some laborers walking very long to eat at home or to warm up in winter.  If I build a house close to a Quarry or a Mine, will Stonecutters or Miners move automatically to this house to avoid long walking distances between the workplace and home?  Or can I assign some citizens to houses closer to their workplace? I have a list of tuples like this:  [ ('a', 1), ('a', 2), ('a', 3), ('b', 1), ('b', 2), ('c', 1), ]   I want to iterate through this keying by the first item, so, for example, I could print something like this:  a 1 2 3 b 1 2 c 1   How would I go about doing this without keeping an item to track whether the first item is the same as I loop around the tuples? This feels rather messy (plus I have to sort the list to start with)... GCD of the already GCD How do I get started creating an Ubuntu Desktop App? I want to create an Ubuntu desktop app, specifically to replace Gwibber.  I can code in Java, Python and a few other technologies. Adobe Flex would have been an option until Adobe decided to suck some more and stopped support for AIR on Linux.  Note - I don't care about supporting other OS's. It will be a personal Ubuntu specific app. It can I open-source, I don't mind extra help.  It should integrate seamlessly with Ubuntu, notifications and all.  I guess Python it is, is that correct? How do I get started? Get last insert id after a prepared insert with PDO Why can't a union of two intervals be the maximum existence interval of a solution? Assume the IVP $$ x'=x^2, \quad x(0)=1 $$ By separating the variables and using the initial condition $$ x(t)=(1-t)^{-1} $$ Then, my book states that since $x_0=1&gt;0$ then the solution can only be extended to the left with maximum existence interval $\, I=(-\infty,1)$.   My question is, since the solution $x(t)$ we found is defined for every $t\neq1$, why isn't the maximum interval of its existence $I^*=(-\infty,1)\cup(1,+\infty)$? Why does it depend on the sign of $x_0$? How can I use an align environment flush left? Is there a way possible to imitate the align environment for math mode commands, without having all writing being placed toward the center on the output page?  MWE:  \documentclass{article} \usepackage{mathtools}  \begin{document} \begin{align*} \cos\theta_1 \cos\theta_2-\sin\theta_1\sin\theta_2 &amp;= \cos(\theta_1 +\theta_2) \\ \sin\theta_1 \cos\theta_2 + \cos\theta_1 \sin\theta_2 &amp;= \sin(\theta_1+\theta_2) \end{align*}  \end{document} Let $trcA=0$.why $A=M+N$ where $M$ and $N$ are nilpotent matrices? Proxy setting for R In what order do multiple readied actions with the same trigger resolve? There is no or there was no I read a sentence in an exam:     There is no child who did not bring his parents to the picnic.    I think that the sentence does not have tense-agreement. Why is is used instead of was? Please explain it to me. Simple bijection $\mathbb N_0 \times \mathbb N_0 \to \mathbb N_0$ I'm looking for a 'simple' bijection $$ \pi \colon \mathbb N_0 \times \mathbb N_0 \to \mathbb N_0, $$  where 'simple' in this context means that it should be as easy as possible to define and it should be self-evident that said function is in fact a bijection. It's a quest for convenience - not minimal complexity in any rigorous sense.  Here are a couple of examples I came up with - none of which satisfy both requirements:   Let $\pi(m,n) = c(2^m3^{n+1})$, where $c \colon \{2^m3^{n+1} \mid m,n \in \mathbb N_0 \}\to \mathbb N_0$ is the order isomorphism (or in fact Mostowski collapse) of its domain under the natural ordering, Let $\pi(m,n) = \langle n,m \rangle$ - Gödel's pairing function, Let $\pi(m,n) = m \oplus n$ - the number resulting from '' $m,n$ (where we imagine both $m$ and $n$ as in infinite decks of cards whose $i$th element is labeled with its respective $i$th digit). ... Is it possible to restart the unity panel without restarting compiz? I'm being hit (quite often) by that bug where you can't click on some indicators. It's easy to fix by restarting unity, but that usually also means running to the risk of upsetting some window on re-parenting (rare, but I'd rather avoid any such problems).  So, I know there is `unity-panel-service', and I'm guessing this might have something to do with the solution?  Is it possible to restart the unity panel (or the entire unity plugin) without restarting compiz itself? I know that packages installed with apt-get are stored in /var/cache/apt/archives.  I just installed mariadb server in Ubuntu 16.04 with following command:  sudo apt install mariadb-server   When I tried to find packages in /var/cache/apt/archives, there are no packages. Where are they stored if it's not in this directory? How can one have a mini table of contents for the current chapter appear just after the chapter name listing all sections of that chapter? Use of Predictable Network Interface Names with alternate kernels Almost constantly, I use kernels from the , or kernels I have compiled myself, using the Ubuntu kernel configuration.  The problem is when I am using the stock kernel it seems to default to using predictable network interface names (i.e. "p4p1"), but when I use any alternate kernel it seems to default to using the old method (i.e. "eth0").  While not really relevant to this question, I had a hard disk failure on my test computer and am doing a new install of Ubuntu Server 14.04.2.  I have not been able to determine what is the difference between the kernels. I suspect a kernel configuration parameter, but have been unable to identify which one.  My question: How can I make predictable network interface names work consistently across all kernels?  Additional notes: Somewhere I saw to disable predictable network interface names to add this to grub:  GRUB_CMDLINE_LINUX_DEFAULT="net.ifnames=0 biosdevname=0"   so, I thought the opposite might help:  GRUB_CMDLINE_LINUX_DEFAULT="net.ifnames=1 biosdevname=1"   but it made no difference. Actually, I can never get the non-stock kernel to use biosdevname, no matter the setting. And I can never get the stock kernel to generate a /etc/udev/rules.d/70-persistent-net.rules file (even though, that is not what I want), no matter the setting of net.ifnames. If I have net.ifnames=1, then at least the non-stock kernel doesn't generate an incorrect /etc/udev/rules.d/70-persistent-net.rules file.  Excerpts from /var/log/udev: stock kernel:  KERNEL[9.216730] add      /devices/pci0000:00/0000:00:1c.4/0000:03:00.0/net/p4p1 (net) ACTION=add DEVPATH=/devices/pci0000:00/0000:00:1c.4/0000:03:00.0/net/p4p1 IFINDEX=2 INTERFACE=p4p1 SEQNUM=1945 SUBSYSTEM=net ... UDEV  [9.241073] add      /devices/pci0000:00/0000:00:1c.4/0000:03:00.0/net/p4p1 (net) ACTION=add DEVPATH=/devices/pci0000:00/0000:00:1c.4/0000:03:00.0/net/p4p1 ID_BUS=pci ID_MODEL_FROM_DATABASE=P8P67 and other motherboards ID_MODEL_ID=0x8168 ID_NET_NAME_MAC=enxf46d04652d8e ID_NET_NAME_PATH=enp3s0 ID_OUI_FROM_DATABASE=ASUSTek COMPUTER INC. ID_PCI_CLASS_FROM_DATABASE=Network controller ID_PCI_SUBCLASS_FROM_DATABASE=Ethernet controller ID_VENDOR_FROM_DATABASE=Realtek Semiconductor Co., Ltd. ID_VENDOR_ID=0x10ec IFINDEX=2 INTERFACE=p4p1   From Ubuntu PPA kernel 4.1RC5:  KERNEL[10.772566] add      /devices/pci0000:00/0000:00:1c.4/0000:03:00.0/net/eth0 (net) ACTION=add DEVPATH=/devices/pci0000:00/0000:00:1c.4/0000:03:00.0/net/eth0 IFINDEX=2 INTERFACE=eth0 SEQNUM=1962 SUBSYSTEM=net ... UDEV  [11.185866] add      /devices/pci0000:00/0000:00:1c.4/0000:03:00.0/net/eth0 (net) ACTION=add DEVPATH=/devices/pci0000:00/0000:00:1c.4/0000:03:00.0/net/eth0 ID_BUS=pci ID_MODEL_FROM_DATABASE=P8P67 and other motherboards ID_MODEL_ID=0x8168 ID_NET_NAME_MAC=enxf46d04652d8e ID_NET_NAME_PATH=enp3s0 ID_OUI_FROM_DATABASE=ASUSTek COMPUTER INC. ID_PCI_CLASS_FROM_DATABASE=Network controller ID_PCI_SUBCLASS_FROM_DATABASE=Ethernet controller ID_VENDOR_FROM_DATABASE=Realtek Semiconductor Co., Ltd. ID_VENDOR_ID=0x10ec IFINDEX=2 INTERFACE=eth0 SEQNUM=1962 SUBSYSTEM=net USEC_INITIALIZED=3227   Note: I have temporarily moved past this issue by allowing a /etc/udev/rules.d/70-persistent-net.rules file to be created, and then editing it for proper device names. Ultimately, I would like to get rid of the file. According to the , you can harden a MySQL server by adding passwords, or removing the anonymous accounts.      If you want to prevent clients from connecting as anonymous users   without a password, you should either assign a password to each   anonymous account or else remove the accounts.   Before hardening, my users table looked like this.   mysql&gt; select user,host,password from mysql.user; +------------------+-----------+-------------------------------------------+ | user             | host      | password                                  | +------------------+-----------+-------------------------------------------+ | root             | localhost | *F3A2A51A9B0F2BE246XXXXXXXXXXXXXXXXXXXXXX | | root             | gitlab    |                                           | | root             | 127.0.0.1 |                                           | | root             | ::1       |                                           | |                  | localhost |                                           | |                  | gitlab    |                                           | | debian-sys-maint | localhost | *95C1BF709B26A5BAXXXXXXXXXXXXXXXXXXXXXXXX | | myuser           | localhost | *6C8989366EAF75BB6XXXXXXXXXXXXXXXXXXXXXXX | +------------------+-----------+-------------------------------------------+   I've remove all anonymous accounts, so that the user table now looks like this.  (I'm using puppet to manage the users, but puppet effectively performs a DROP USER command).   mysql&gt; select user,host,password from mysql.user; +------------------+-----------+-------------------------------------------+ | user             | host      | password                                  | +------------------+-----------+-------------------------------------------+ | root             | localhost | *F3A2A51A9B0F2BE246XXXXXXXXXXXXXXXXXXXXXX | | debian-sys-maint | localhost | *95C1BF709B26A5BAXXXXXXXXXXXXXXXXXXXXXXXX | | myuser           | localhost | *6C8989366EAF75BB6XXXXXXXXXXXXXXXXXXXXXXX | +------------------+-----------+-------------------------------------------+   Why is it that I am still able to login to my test system without a username or a password? What do I need to do to prevent any unwanted users from logging in?   root@gitlab:~# mysql Welcome to the MySQL monitor.  Commands end with ; or \g. Your MySQL connection id is 98 Server version: 5.5.32-0ubuntu0.12.04.1 (Ubuntu) .... mysql&gt;    Update:  I've also just discovered that I can login as root, without entering a password.  Update2: I found  which has some good information, but does not solve the issue.   There are no anonymous users.  mysql&gt; select user,host,password from mysql.user where user=''; Empty set (0.00 sec)   I login as root@localhost.  mysql&gt; select USER(),CURRENT_USER(); +----------------+----------------+ | USER()         | CURRENT_USER() | +----------------+----------------+ | root@localhost | root@localhost | +----------------+----------------+    I do not have a default password, or skip-grant-tables defined in my.cnf  root@gitlab:~# cat /etc/mysql/my.cnf |grep -i 'skip-grant-tables'|wc -l 0 root@gitlab:~# cat /etc/mysql/my.cnf |grep -i 'pass'|wc -l 0   Update3:  I have tried performing these steps with puppet, (which should perform a flush privileges automatically). I have also manually flushed privileges and also tried restarting mysql.   Update4: I've also tried changing the mysql root password and flushed privileges. No luck, I can still log in as any user without a password. Black nontransparent glass (Cycles) I am modeling plane and I don't want to model a cockpit so I want to use black windows which will reflect a lot of light but you can't see thought.   Currently I just use Glossy BSDF (GGX) with almost black color (0.01, 0.01, 0.01) and Rougness 0.015 but it don't look quite right. It lacks glass shine and looks too matt.  Edit:  Here is my simplified blend file:    Also here is what i want. Glass on this tie fighter is blackish and it looks like glass. In my blend file it looks more like plastic.    One more thing i noticed is when light reflect from glass whole glass section reflect same amount of light. It can be seen on tie fighter example above. How would I give a simple example of a function $f$ differentiable in a deleted neighborhood of $x_0$ such that $\lim_{x\to x_0}f^\prime(x)$ does not exist? I cannot seem to think of an example.  A delete neighborhood is an open interval about $x_0$ which does not contain $x_0$. So, $(x_0-\delta,x_0+\delta)-\{x_0\}$ for some $\delta&gt;0$.  How would something be differentiable in a deleted neighborhood if at the point of the derivative, the limit does not exist. Presumably, the derivative ends up looking something like $\lim_{x\to x_0} \dfrac{1}{x}$, if it does not exist. In plain English, how does casting spells and using creature abilities work with the stack and priority? I'm a relatively new player to Magic: the Gathering. I was reading  to try to understand exactly when it's okay to cast instants (e.g. ) and use some abilities (e.g.  should be tappable sometime during other peoples' turns), but I don't seem to be making much progress: as I come to understand some things, others make less sense.  My confusion is boundless  For instance: to cast  one needs priority. Spells go on the stack, and priority gets passed at some points (I have no idea when), and effects on the stack are resolved when both players have passed priority. But when is that? I can't find any mention of when the other player gets the priority to cast an instant, except on their own turn. Furthermore,  states that during the Main Phase:     505.4. Second, the active player gets priority. Players may cast spells and activate abilities. The active player may play a land.   So players (plural) may cast spells, but only the active player has priority, so only the active player can cast an instant. The turn rules, and the rules on , never mention any point at which the other player gets priority, so when can they possibly Cancel?  In addition, you can only cast a spell when the stack is empty, so the entire stack must be able to be resolved in your turn at some point.  I need an explanation!  I could go on a bit more. There is also  which can be overloaded to "Counter each spell you don't control", which seems like it could only possibly work with an understanding of the stack.  Could someone explain, in simple English:   When can Instants be cast? When can tap abilities be used? What do Instants and abilities have to do with the Stack and Priority?