If they are needing to get back into USA is an eBay card actually helping them or is it a scam
On Travel.SE we often see questions about a person (usually a love interest) asking for money to pay for airfare, visas, permits and other expenses. For example        What general advice can be given in such situations to the person asking the question? Is it all a scam or can there be legitimate situations in which an online friend could be asking for money?
Express $\sqrt{3}\sin\theta - \cos\theta$ as: $a\cos (\theta + \alpha) $ Express $\sqrt{3}\sin\theta - \cos\theta$ as: $a\cos (\theta + \alpha) $  Can someone please explain to me how to go about doing this? Determine if a set of tiles on a grid forms an enclosed shape How to force NSLocalizedString to use a specific language In an ideal circuit, How can there be a current b/w points a &amp; b, when there is no potential difference and thus no electric field between a &amp; b? If there is no current, then where does current across the resistor come from, because that means no charge is coming from the battery (?). I dual booted ubuntu 11.04/11.10 a while ago with a USB stick and i want to uninstall it.   I would like to completely uninstall the old version and get 12.04.  I have a 64 bit laptop. Please help! I am just a high school student, and I haven't seen much in mathematics (calculus and abstract algebra).  Mathematics is a system of axioms which you choose yourself for a set of undefined entities, such that those entities satisfy certain basic rules you laid down in the first place on your own.  Now using these laid-down rules and a set of other rules for a subject called logic which was established similarly, you define certain quantities and name them using the undefined entities and then go on to prove certain statements called theorems.  Now what is a proof exactly? Suppose in an exam, I am asked to prove Pythagoras' theorem. Then I prove it using only one certain system of axioms and logic. It isn't proved in all the axiom-systems in which it could possibly hold true, and what stops me from making another set of axioms that have Pythagoras' theorem as an axiom, and then just state in my system/exam "this is an axiom, hence can't be proven".  EDIT : How is the term "wrong" defined in mathematics then ? You can say that proving fermat's last theorem using the number-theory axioms was a difficult task but then it can be taken as an axiom in another set of axioms .  Is mathematics as rigorous and as thought-through as it is believed and expected to be ? It seems to me that there many loopholes in problems as well as the subject in-itself, but there is a false backbone of rigour that seems true until you start questioning the very fundamentals . Probability of area being greater than 0.5 with random lines The muffins were rock hard, what did I do wrong? Frequency of the sound when blowing in a bottle I'm sure you have tried sometime to make a sound by blowing in an empty bottle. Of course, the tone/frequency of the sound modifies if the bottle changes its shape, volume, etc.   I am interested in understanding how the tone/frequency of this sound can be (approximately) calculated from the shape of the bottle. Is there some formula?  If you have any references about this please post them in your answers.  Being a mathematician I keep hearing that the principal tone is given by the first eigenvalue of the Laplace operator, and I'd like to understand the physical explanation. Gaming the system for Populist badges Installation problem QGIS I do not manage to install QGIS on my windows 10 machine using the osgeo4w installer.  During the installation I get this message:   At the end of the installation I get this message:   And when I subsequently try to run QGIS, I receive this message:    Similar issue can be found in various fora, but none of them provides a conluding answer or did help me to solve the problem.  Any propositions? how to replace multiple strings together in Oracle Prove that if $\sum{a_n}$ converges absolutely, then $\sum{a_n^2}$ converges absolutely I'm trying to re-learn my undergrad math, and I'm using Stephen Abbot's Understanding Analysis. In section 2.7, he has the following exercise:  Exercise 2.7.5 (a) Show that if $\sum{a_n}$ converges absolutely, then $\sum{a_n^2}$ also converges absolutely. Does this proposition hold without absolute convergence?  I'm posting about this here because my answer to that last question about whether the proposition holds without absolute convergence is "Yes", but my suspicions are raised by him merely asking the question. Usually questions like this are asked to point out that certain conditions are necessary in the statement of propositions, theorems, etc. I just want to see if I'm missing something here.  Anyway, here's how I prove the absolute convergence of $\sum{a_n^2}$, and note that I never use the fact that $\sum{a_n}$ is absolutely convergent:  Proof: Let $s_n = \sum_{i=1}^n{a_n^2}$. I want to show that $(s_n)$ is a Cauchy sequence. So, let $\epsilon &gt; 0$ and $n &gt; m$, and consider, \begin{equation}   \begin{aligned}     |s_n - s_m| &amp;= |(a_1^2 + a_2^2 + \cdots a_n^2) - (a_1^2 + a_2^2 + \cdots a_m^2)|\\                 &amp;= |(a_{m+1})^2 + (a_{m+2})^2 + \cdots + a_n^2|\\                 &amp;= |a_{m+1}|^2 + |a_{m+2}|^2 + \cdots + |a_n|^2\\   \end{aligned} \end{equation} Now, since $\sum{a_m}$ converges, the sequence $(a_m)$ has limit 0. Therefore I can choose an $N$ such that $|a_m| &lt; \sqrt{\epsilon/n}$ for all $m &gt; N$. So for all $n &gt; m&gt; N$,  we have, \begin{equation}   \begin{aligned}     |s_n - s_m| &amp;= |a_{m+1}|^2 + |a_{m+2}|^2 + \cdots + |a_n|^2\\                 &amp;&lt; \left(\sqrt{\frac{\epsilon}{n}}\right)^2 + \left(\sqrt{\frac{\epsilon}{n}}\right)^2 + \cdots + \left(\sqrt{\frac{\epsilon}{n}}\right)^2\\                 &amp;&lt; \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2 + \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2 + \cdots + \left(\sqrt{\frac{\epsilon}{n-m}}\right)^2\\                 &amp;= \epsilon   \end{aligned} \end{equation} Therefore $(s_n)$ is Cauchy and $\sum{a_n^2}$ converges. And since $\sum{a_n^2} = \sum{|a_n^2|}$, the series $\sum{a_n^2}$ is absolutely convergent. &#x220E;  Am I doing something wrong here? Am I right in thinking that $\sum{a_n}$ need not be absolutely convergent for $\sum{a_n^2}$ to be absolutely convergent? I'm currently reading documentation about map projections to understand the source code of the Proj4 project.  The scale factor is named in a variety of sources I read. This sources explained its definition and its value for some projections.   In the source code of Proj4, for the mercator projection (sphere and ellipse case), the scale factor influences the coordinates on the projection :   //P-&gt;k0 is the scale factor xy.x = P-&gt;k0 * lp.lam; xy.y = - P-&gt;k0 * log(pj_tsfn(lp.phi, sin(lp.phi), P-&gt;e));   Why and how I should use the scale factor during the computation of the projection ? Is there any valuable resources on the web ?  This question in asked in the sense of projection computation. I can find the formula for the inverse and forward projection as well as the scale factor in a various of resources, but no one explains how I should use both in a algorithm. You have the definition of the projection and the definition of the scale factor, but it's not clearly written that I should multiply or divide the result by the scale factor.   Is it a general rule : if I find the formula for any projection with the related scale factor, should I, in all cases, always divide or multiply the results by the scale factor ? Some months ago I posted  about exporting Sentinel 1 scenes from a collection and was successful with help from .   I now have a new region of interest, which sits on the overlap between 2 scene footprints (sequential images in descending orbit). When I make a mosaic of the 2 scenes I get a small no data gap and lack of alignment between the 2 images:  // Create a geometry representing an export region. var roi = ee.Geometry.Rectangle([-62.67, -8.31, -63.25, -8.85]); var zoomPoint = ee.Geometry.Point([-62.35, -8.06])  // Load the Sentinel-1 ImageCollection. var sentinel1 = ee.ImageCollection('COPERNICUS/S1_GRD') .filterBounds(roi);   // Filter by metadata properties. var IW_H = sentinel1  // Filter to get images with VV and VH dual polarization. .filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VV')) .filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VH'))  // Filter to get images collected in interferometric wide swath mode. .filter(ee.Filter.eq('instrumentMode', 'IW'))  // Filter IWs to get High res. .filter(ee.Filter.eq('resolution', 'H'))  // Filter IW-Highs to get 10m res .filter(ee.Filter.eq('resolution_meters', 10));  // Filter to get images from different look angles var col_desc = IW_H.filter(ee.Filter.eq('orbitProperties_pass', 'DESCENDING'));  // Spatially mosaic the images in the collection and display var col = col_desc.mosaic(); var colVV = col.select(0) Map.addLayer(colVV, {min:-17, max:-3}, "VV"); Map.centerObject(zoomPoint, 20);   What am I missing?  Are these scenes not acquired sequentially? How do you add a timed delay to a C++ program? I am trying to add a timed delay in a C++ program, and was wondering if anyone has any suggestions on what I can try or information I can look at?  I wish I had more details on how I am implementing this timed delay, but until I have more information on how to add a timed delay I am not sure on how I should even attempt to implement this. "Have you seen her?" or "Did you see her?" I already knew that we use the present perfect for an action in the past with a result now. Consider the following questions:   "I'm looking for Paula. Have you seen her?" "I'm looking for Paula. Did you see her?"   Is there any difference between these two questions for this specific action (verb)? What is the result of "seeing" action which can't be represented by simple past? I would like footnote numbering to continue over pages and chapters. In my document it's reset every chapter. I'm using the report documentclass. "This one is" OR "This is" I have seen people using "This one is Daddy's" with the word "one" before a form of the verb be. I am confused about which is more accurate, to use:     This is Daddy's.   or     This one is Daddy's.   Hope you can address my concerns, thank you. How do I calculate someone's age based on a DateTime type birthday?