I booked a round-trip flight for me and my wife from Egypt to Los Angeles for a family visit. I had to stay longer in LA than previously planned. However my wife should get back PLUS my mother-in-law.  Is there any way my mother-in-law can replace me on the return flight?
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.
How to draw tangent vectors and component vectors on a curve I am searching for a way to have a figure drawn using LaTeX. I am aware of some packages TikZ and PSTricks that could accomplish this, and have been tinkering around with them recently but do not have enough skill set at the moment to accomplish this drawing. Is there a way someone can accomplish the drawing, preferably with TikZ but could be any package your most comfortable with in a reduced amount of coding (non-advanced) to where I could understand what is happening from the code to the picture. If this is not possible, then I will have to study the package more and work with it until I understand the method (code) to create the graphic. The drawing is below.  Note: This is a rough sketch. The optimal output would have smooth quadratic curves and all quantities are vectors. Multiple Inheritance in C# "For security reasons, framing is not allowed; click OK to remove the frames." on Imgur upload Ok first, there's that lugubrious use of the semicolon; not necessary.  Second, I didn't open a frame!  You did!  Alls I tried to do is upload a 5MB animated .gif file via Imgur.    Looking further into this, Imgur actually posts an error when you upload an animated .gif larger than 2MB.    Go figure! I want to add a check constraint on a column if entered value for column is greater than 3 than it should be saved as 1 else entered value. For that scenario I am using below query but on insertion of data it shows an error message.  create table tblTestCheckConstraint  ( id int, NewColumn int )   alter table tblTestCheckConstraint add constraint chk_tblTestCheckConstraint_NewColumn1 CHECK   (     CASE         WHEN NewColumn &gt;4 THEN 1         ELSE NewColumn     END = 1 )   Insert Statement:   insert into tblTestCheckConstraint values ( 1,5) insert into tblTestCheckConstraint values ( 1,2)   Error Message:   Msg 547, Level 16, State 0, Line 1 The INSERT statement conflicted with the CHECK constraint "chk_tblTestCheckConstraint_NewColumn1". The conflict occurred in database "DBName" , table "dbo.tblTestCheckConstraint", column 'NewColumn'. The statement has been terminated. Going to Pakistan in 3 weeks time but my NICOP is expired and my son's hasn't arrived yet My NICOP is expired and I have already booked a flight to Pakistan via Qatar Airways. My wife has a valid NICOP card but my 5 years old child  has never had a NICOP or any other Pakistani ID card other than the British passport. I have made an appointment for next Monday to renew my NICOP and apply for my child's new NICOP card. My question is, what if the cards of my child and mine don't arrive in time, can we still travel to Pakistan, given that we have the receipts as a proof of application? Normalizing point cloud data How I can get Digital Height Model (only object heights, DSM - DTM = DHM)?  Many applications can do this, but they convert it to GRID or TIN format. I was wondering if it was possible to keep the data as point clouds. If object A is moving at velocity $v$ (normalized so that $c=1$) relative to a ground observer emits object B at velocity $w$ relative to A, the velocity of B relative to the ground observer is  $$ v \oplus w = \frac{v+w}{1+vw} $$  As expected, $v \oplus 1 = 1$,  as "nothing can go faster than light".  Similarly, $v \oplus -1 = -1$. (same thing in the other direction)  But what if object A is moving at the speed of light and emits object B at the speed of light in the exact opposite direction? In other words, what is the value of $$1 \oplus -1?$$ Putting the values in the formula yields the indeterminate form $\frac{0}{0}$. This invites making sense of things by taking a limit, but $$ \lim_{(v,w)\to (1,-1)} \frac{v+w}{1+vw}$$ is not well-defined, because the limit depends on the path taken.  So what would the ground observer see? Is this even a meaningful question?  Edit: I understand $1 \oplus -1$ doesn't make sense mathematically (thought I made it clear above!), I'm asking what would happen physically. I'm getting the sense that my fears were correct, it's physically a nonsensical situation. What is some good free software for doing physics calculations?  I'm mainly interested in symbolic computation (something like Mathematica, but free). How to install Python 3.6? When should I upgrade my camera body? The projection of an ellipse is still an ellipse While studying the problem of determining the orbit of a binary star system, my astronomy notes say: "the projection of an ellipse onto a plane is still an ellipse (except the special case in which it's a segment)". How could I prove this?  EDIT: As suggested i'm adding what I know about ellipses. I know the basics of ellipses in the plane, the equation of an ellipse in a plane in cartesia coordinates, the equation of an ellipse in polar coordinates, the fact that ellipses can be obtained by the intersection of planes with a cone. In my geometry course we defined ellipses as the the points of the plane such that the ratio between the distance from a point and a line is constant and less than 1. I also know that the sum of the distances of the points of the ellipse from the foci is constant. How to extract and install .deb without the command dpkg? I am running Debian jessie stable in order to understand how the .deb package interacts with the system. What is the correct way to extract and install a packge_name.deb without the command dpkg? Derived template-class access to base-class member-data How does gravity work on Serenity? When the good ship Serenity is traveling in deep space, the crew experiences what looks like an Earth-normal (or Earth That Was-normal) level of gravity. Is it ever explained how the ship is able to generate artificial gravity? The ship doesn't spin, so  is out.  is a possibility, but I think the gravity in the ship pulls in a direction that is perpendicular to the direction the ship is usually traveling in, not opposite, like this method would require.   So: how does she pull it off?   Extra credit: how does she pull it off in the episode ? Serenity's engine is totally dead, to the extent where not even life support systems are online. Yet Mal still has to valiantly haul himself around on the floor to replace the compression coil, so whatever creates the artificial gravity on Serenity is clearly still going. How? PHP: How do you determine every Nth iteration of a loop? How to print object content in correct way? Cannot log into Area 51 with OpenID How to get the ASCII value of a character I've discovered a rather weird behaviour of PdfLaTeX. In this example  \documentclass{article} \usepackage[breaklinks]{hyperref} \begin{document} \url{http://www.emarketer.com/blog/index.php/quick-stat-smartphone-users-account-38-mobile-phone-users/} \end{document}   PdfLaTeX won't break the URL and create a too long line. However, if I replace \url with \href like this:  \documentclass{article} \usepackage{hyperref} \begin{document} \href{http://www.emarketer.com/blog/index.php/quick-stat-smartphone-users-account-38-mobile-phone-users/}{http://www.emarketer.com/blog/index.php/quick-stat-smartphone-users-account-38-mobile-phone-users/} \end{document}   I get the line broken, but the font of the link is not right any more of course (normal instead of texttt). Why doesn't URL break the line at dashes and what could I do to get a nicely typeset line-broken link? I'm looking for a source/spec that can tell me what CSS properties can applied to which HTML elements.  For instance, the css property; "overflow".  I know I can apply this to div, p, textarea but what other elements can I apply this too?  Is there a spec somewhere I can reference?