Unexpected Characters after using \cal
Why does \cal{M}_n give “M>”?
Proof of a formula involving Euler's totient function: $\varphi (mn) = \varphi (m) \varphi (n) \cdot \frac{d}{\varphi (d)}$ List files in a specific folder in a document library I there anyway to output the files of a specific folder in a document library?  Listing them will be like   foreach $file in $folder.files {     write-host $file.name }    But how do I tell it to look a specific folder? In CSOM please Tried the below answer but it did not work Proof by induction that if $n \in \mathbb N$ then it can be written as sum of different Fibonacci numbers Proof that every natural number $n\in \mathbb N$, can be written as the sum of different Fibonacci numbers between $F_2,F_3,\ldots,F_k,\ldots$.  For example: $32 = 21 + 8+3 = F_8+F_6+F_4$  Research effort:  The base step it's simple:  Let $k=1$ it can be britten as $k=1=F_2$  For the inductive step I considered:  Let $k = k  F_2 =F_2+F_2+\cdots+F_2 = \sum_{i=2}^w a_iF_i, a_i =\{0,1\} $  Then if $k$ suffice I want to see if $k+1$ suffices too... But I'm not realy seeing how to use the inductive hypothesis, so I assume It's wrong.  Any thoughts on which can the inductive step be? 1.35 V RAM in a 1.5 V system - Will it fry or overclock? The general question is: When installing low voltage RAM in a board that outputs a higher voltage to the memory module, will this fry the RAM or will it be like overclocking it?  My specific case is: I have the Alienware m17xR3 laptop with a 2630QM Sandy Bridge board. Currently, I have the stock 1.5 V modules and when I check the overclocking options in my bios, the RAM voltage option ranges from 1.5 - 1.65 V. Is this simply because the bios recognizes that these are the values which my current RAM support and thus they will change when I install 1.35 V RAM or will I have to run the 1.35 V sticks at minimum 1.5 V?  If the case is the latter, would I fry my 1.35 V sticks? Or would they become automatically overclocked and get tighter timings with a higher voltage? Or both? Or neither? I'm a bit lost :p Difference between "commit suicide" and "suicide" I have an image that is Base64 encoded. What is the best way to decode that in Java? Hopefully using only the libraries included with Sun Java 6. Log-transformed variable is not significant, while variable itself is I'm doing a Logistic Regression on company level using the total assets to control for company size. Due to the skewedness of the data, I do a log-transformation of the asset data. While I get no significance for the log-transformed variable, the not transformed variable is highly significant (p &lt; 0.01). What could be a possible explanation of such a result? Does it mean that the relationship is not diminishing for extremely high and low values or does it show an outlier problem and should not be used for interpretation of the data. Enter from password field doesn't submit SE login form On  page for a site where I don't yet have an account, if I select the "Log in using Stack Exchange" box, when I hit enter from the password form, nothing happens.  Minor, but... I am trying to really understand why the gradient of a function gives the direction of steepest ascent intuitively.  Assuming that the function is differentiable at the point in question, a) I had a look at a few resources online and also looked at this   , a popular question on this stackexchange site. The accepted answer basically says that we multiply the gradient with an arbitrary vector and then say that the product is maximum when the vector points in the same direction as the gradient? This to me really does not answer the question, but it has 31 upvotes so can someone please point out what I am obviously missing?  b) Does the gradient of a function tell us a way to reach the maxima or minima? if yes, then how and which one - maxima or minima or both? Edit: I read the gradient descent algorithm and that answers this part of my question.  c) Since gradient is a feature of the function at some particular point - am I right in assuming that it can only point to the local maxima or minima? Class imbalance strategies When dealing with the class imbalance problem in a binary classifier, there are three ways I know of to address it: over-sampling, under-sampling and using cost-sensitive methods.   Are there any guidelines, rules of thumb or general strategies to choose among these methods? A possible answer would be: over-sample when the positive class has more than 100 instances (I just made it up). What is a Generic Handler in asp.net and its use? Can two PS4s log in to the same PSN account? Both myself and my boyfriend have PS4s.  Can I just get a single PSN account and sign both consoles into the same account, or do I need to get two separate accounts? Copy skype chat history to text files? I'd like to convert my Skype chat history to a collection of text files for archival purposes.  Ideally, I'd like to have a command (e.g. script or app) so that I could do this on a regular basis.  Any one have any idea on how to go about doing this? If $f(x)\to 0$ as $x\to\infty$ and $f''$ is bounded, show that $f'(x)\to0$ as $x\to\infty$ Let $f\colon\mathbb R\to\mathbb R$ be twice differentiable with $f(x)\to 0$ as $x\to\infty$ and $f''$ bounded. Show that $f'(x)\to0$ as $x\to\infty$. (This is inspired by  to a different question) What is the best collation to use for MySQL with PHP? I'm wondering if there is a "best" choice for collation in MySQL for a general website where you aren't 100% sure of what will be entered? I understand that all the encodings should be the same, such as MySQL, Apache, the HTML and anything inside PHP.  In the past I have set PHP to output in "UTF-8", but which collation does this match in MySQL? I'm thinking it's one of the UTF-8 ones, but I have used utf8_unicode_ci, utf8_general_ci, and utf8_bin before. Does the 90 days VWP rule expire if you travel from the US to Canada? I'm on a New Zealand passport.  From most US Embassy webpages:     The Visa Waiver Program (VWP) enables nationals of certain countries,   including Australia, New Zealand, and the U.K., to travel to the   United States for tourism or business for stays of 90 days or less   without obtaining a visa, if certain requirements are met. Under the   VWP, time spent in Canada, Mexico, and adjacent islands counts towards   the maximum of 90 days stay allowed under the program.   I'll be there on a 1-year working holiday visa starting when I arrive in Vancouver. I'm spending 3 days in Hawaii en route to Vancouver. This seems to imply that 90 days after landing in Hawaii, my time will be up and I won't be able to get back into the US, as my living in Canada will not reset the clock. What if after this time I want to say, pop across the border to Seattle? How can I restart the 90 days, without having to resort to say, flying to Japan and back just to reset it? How to replace subscript symbols I used python add in to make a tool bar in Arcmap that edits features on a map. It works on a file geodatabase, but not on an ArcSDE version one. I've been getting an FDO error: 0. The solutions that I've found all involve opening a workspace, but I'm getting an error doing that as well. Here is the relevant portion of my code:          outFolderPath = r"U:\tempStuff"         outName = "Stuff.sde"         databasePlatform = "SQL_Server"         instance = "SQL Server"         arcpy.CreateDatabaseConnection_management(outFolderPath, outName,                                                   databasePlatform,                                                   instance)         print "Centroid of buidling:(%r,%r) Side length: %r" % (xCoordinate,                                                                 yCoordinate,                                                                 bob)         print "workspace is %r" % outName #outName is workspace          #Start edit session with an undo/redo stack then start         #edit operation         print "Starting editing"         edit = arcpy.da.Editor(outName) #outName is workspace Line 86         edit.startEditing(True, True)         edit.startOperation()          #stuff happens          cursor = arcpy.da.InsertCursor( fc, ["SHAPE@"])         cursor.insertRow([stuff])             #stop the edit operation and then save changes         edit.stopOperation()         edit.stopEditing(True)          del cursor         print "Building should be drawn"   This is the exact error I've been getting:  Traceback (most recent call last):   File "C:\Users\153289\AppData\Local\ESRI\Desktop10.3\AssemblyCache\{0BEF4E61-6332-4BCA-A908-959CA3C0B4E7}\leetScripts_addin.py", line 86, in onClick     edit = arcpy.da.Editor(outName)#outName is workspace RuntimeError: cannot open workspace   What's am I doing wrong in my code? Fibonacci proof question: $f_{n+1}f_{n-1}-f_n^2=(-1)^n$ There have been several discussions regarding code-only answers (answers that contain only code blocks with no textual explanation whatsoever):         Personally, I can't see why the quality filter should let such answers through at all. The main problem I have with code-only answers, especially once they're flagged as not an answer or very low quality, is that we can't determine at a glance whether these answers are:   Genuinely attempting to answer the question  answers Trying to correct an error in the question without actually answering it Random code dumps that may or may not relate to the question even by programming language or keyword(s) in the question   In particular, what exactly is an "informative code-only answer"? Does it mean the code is self-documenting? Does it mean the code substitutes code comments for a proper write-up? This is all very fuzzy. From  to the last question above:     I have never seen a code-only answer that couldn't be made better with the addition of appropriate text. They are of lower-quality than the same answer with some text.   This text makes all the difference, IMO, between an answer and a non-answer. Without it, it's often needlessly difficult to tell.  Existing code-only answers that are good-faith attempts to answer the question should be edited or downvoted, yes. But if the quality filter already tries to block code-only questions, why not block code-only answers too? These answers are often low quality, and (almost) always have ample room for improvement, just like questions.