Showing $\sum\limits_{i=1}^n\frac1{\sqrt i}>\sqrt n$ by induction.
Use Complete Induction of set theory to prove $\frac{1}{\sqrt{1}} + \frac{1}{\sqrt{2}} + \frac{1}{\sqrt{3}} + ... + \frac{1}{\sqrt{n}} > \sqrt{n}$.
How to sum a variable by group Getting the class name of an instance? How do I find out a name of class that created an instance of an object in Python if the function I am doing this from is the base class of which the class of the instance has been derived?  Was thinking maybe  might have helped me out here, but it doesn't seem to give me what I want. And short of parsing the __class__ member, I'm not sure how to get at this information. Script-r Symbol The near-ubiquitous undergraduate reference on electrodynamics, "Introduction to Electrodynamics" by David Griffiths make extensive use of a script-r symbol, defined to be \vector{\scriptr} \equiv \vector{r} - \vector{r}^{\prime} and looks like:    Although the question of how to produce such a symbol in LaTeX is quite a common one I am yet to find a satisfactory solution.  The closest I've found is from the physymb package and uses the Calligra fonts:    Sadly, there is not a bold variant of this character and it is far more cursive than I would like.  I am hence wondering if there are any better facsimiles. Missing new file in Ubuntu 13.04 The New file operation is missing in Ubuntu 13.04. How can I fix it?  I have only &quot;New Folder&quot;. How can I add the New File option again? Let $p(x)$ be a polynomial of degree $n$ satisfying $p(x)\geq 0$ for all $x$. That is, for all $x$, $p(x) = a_n x^n + a_{n-1} x^{n-1} + \cdots + a_1 x + a_0 \geq 0$, $a_n\neq 0$.  Show that $p(x)+p&#39;(x)+p&#39;&#39;(x)+\cdots+p^{(n)}(x)\geq 0$ for all $x$ where $p^{(i)}(x)$ is the $i^\text{th}$  derivative.  My interest: I know that, we can rewrite the LDE as follows  $$ p(x)+p&#39;(x)+p&#39;&#39;(x)+\cdots+p^{(n)}(x) = Lp(x) $$  where $L := I + D + D^2  + \cdots + D^{(n)}$. Can we say anything about a linear operator of this kind so that it does not change the sign of the input it takes? I can try to solve the question by writing for all the derivatives and factoring them using $p(x)$, but I think there should be a clever way of showing this by the properties of $L$. Can I figure out a solution by just looking at $L$ and the sign of $p(x)$ as in the question? Where should I look for that? Class imbalance in Supervised Machine Learning Proof of $(a+b)^{n+1}$ I have to do proof of $(a+b)^n$ and $(a+b)^{n+1}$ with mathematical induction.  I finished the first one $(a+b)^n = a^n + na^{n-1}b+\dots+b^n$.  I however have trouble with the second one, I don't know what to start exactly. Any help/hints? "dev/sda1: clean, ..." This message appears after I startup my laptop, then it won't continue booting Cannot move file to trash warning when trying to delete a file in Nautilus I am trying to delete files in Nautilus and every time I try to delete one it always gives me this message:     Cannot move file to trash, do you want to delete immediately?   Then it gives me several questions. All I want is that when I press Delete in the keyboard, it sends it automatically to the trash can. Not to ask me every time.  The problem relates to NTFS partitions, external drives but also include Linux filesystems.  What are the reasons for nautilus beeing not able to move to trash? I would like to know if my brother can fly by United Airlines from USA to El Salvador, and my father, from El Salvador to USA using the same round trip ticket, both of them have the same name. Classify all groups with order $pq$, $p$ is not equal to $q$ I am reading the following material:  . At page 5, there is a proof classifying all groups with order $pq$(they are all primes and $p$ is not equal to $q$). I am lost in the last two sentence, which claims the semidirect product are all isomorphic. Could someone help me to understand it? Thanks! When to use unsigned values over signed ones? I have recently installed lubuntu 11.10 on my old laptop (acer aspire 5315 celeron) and observed that fan is not working properly on lubuntu side.I find it strange that it is working perfectly under window vista.   How could I solve this problem? I have a little problem with the placement of my picture. I want to insert it at the end of the introduction chapter but its place is not where I want.   I think the problem become from the:  \begin{figure} ... \end{figure}   Because when I insert the picture without using \begin{figure}... the picture is at the end of the chapter as I want.   Look the picture below. I noticed that the these two commands to list files below 5 GiB produce different results:  find . -type f -size -5368709120c find . -type f -size -5G   Specifically the one that uses kilobyte unit (5368709120c) returns additional files that are larger than the maximum file size returned by the one that uses the GiB unit (5G).  From the find manual page I read the following:  -size n[cwbkMG]           File uses n units of space.  The following suffixes can be used:           `b'    for 512-byte blocks (this is the default if no suffix is used)           `c'    for bytes           `w'    for two-byte words           `k'    for Kilobytes (units of 1024 bytes)           `M'    for Megabytes (units of 1048576 bytes)           `G'    for Gigabytes (units of 1073741824 bytes)  The size does not count indirect blocks, but it does count blocks  in sparse files that are not actually allocated.  Bear in mind that the `%k' and `%b' format specifiers of -printf handle sparse files differently.   The  `b'  suffix always denotes 512-byte blocks and never 1 Kilobyte blocks,  which is different to the behaviour of -ls.   So, given that the unit of G is 1073741824, 5G should be 5368709120c. Is the issue due to how sparse or indirect blocks are counted?  Thanks in advance for the help. What does the helpful flag mean? I don't see "Helpful" in the list of things I can do when I press the flag link.   In my profile page I saw "6 helpful flags."  How do I earn these flags?  May I make them on other peoples' posts or comments?   This is what I am talking about: Several files in my home directory have been disappearing. E.g. .bashrc, .bash_profile, authorized_keys and now .profile.  Regardless of how this happened, I would like to restore the original pristine .profile file. If I create a new user on my system one is created. Where can I find this .profile contents from a fresh, untouched install? USB composite device driver I am wondering if it possible to create a USB device (in following the device) composed from   a custom circuit (eg arduino) and  a flash storage   in such a manner that the device is recognized as a standard usb flash storage (and as such is operable with standart OS drivers), while said storage holds the utilities to operate with the custom circuit (dispalying the data colled by the circuit); and if so, how?  My first thought was to smack a cheap usb-hub and usb-pen before my circuit but that solution, is not pleasing to me.  My goal is to eliminate the need to carry an extra flash-drive just for the operating software, and use default os drivers, make it plug-and-just-work:   i plug the device in the os (windows) mounts a new flash-drive without needing a special driver is start (manually or via autorun) my custom.exe from that flash-drive i recive data measured by the circuit I have a Samsung Galaxy S5 duos with stock Android Marshmallow, and I'm considering encrypting my SD card to prevent access to its contents in case I lose my phone. The main reason of not doing this is that I'm not sure if there's a way to mount an encrypted SD card on Windows (or other desktop OS's)   When I encrypt the SD card on my Samsung Galaxy S5, is it using a known implementation of encryption, or is it something that only works on Android (or perhaps Samsung) phones?   I do not want to use USB connection to my phone to access my SD card, it's terrible. Mounting the SD card is much easier and faster and less annoying.   EDIT: just to clarify, I am NOT talking about adoptable storage. I want a portable encrypted SD card that can both be read on PCs and Android phones (i.e. I want to be able to remove the SD card from my phone, plug it into my PC, provide a password to decrypt and read/write it like any other SD card) Vertical text (not in table)