On page 5 of the titlesec manual (released on June 14, 2000), it is written that full skip values, including the plus and minus parameters can be abbreviated as * n.   The example on page 24-25 (the code I am referring to is actually on page 25) input the following as a full skip value:  1.5ex plus .1ex minus .2ex  Could you please explain what that means and where it is applicable?
There are many lengths in LaTeX. For instance, \enskip, \enspace, \quad, \parskip, \smallskip, ...  Some of them are mostly used for vertical spacing, some others are mostly used for horizontal spacing, and perhaps some of them are used in both cases. I wonder whether there is a list that indicates the meaning and intended use of each length in LaTeX.  By "intended use" I mean not only whether the length is vertical or horizontal, but in which circumstances it is a good practice to use that specific length.
Find polynomials $A(x)$ and $B(x)$ such that $A(x)P(x) + B(x)Q(x) = x + 1$ for all $x$ where $P(x) = x^4 - 1$ and $Q(x) = x^3 + x^2$. I'm stumped on this question. I know that I'm supposed to apply the extended version of Euclid's algorithm for polynomials but I'm unsure of how to do that. I thought about trying to create some kind of linear system but guessing arbitrary coefficients but that wouldn't work as $A$ and $B$ don't have fixed degrees. In viewing the weekly list of rep change, I see  on top: razpeitia2 5 16  member for: 2 years, 7 months link #1 week rank +8529 change 727 total reputation 2,286 week reputation    How can someone with 727 total have 2286 for the week with no bounties?  Call me curious.  Is this a bug or something else here? Can I enter Croatia with single entry visa Schengen? I seem to have run into a bit of a challenge on one of our Android/Samsung devices...   On the device, regardless of what's open, when the battery reaches 25% on discharge, the below screen pops up and covers the entire screen, with MUCH difficulty to get rid of. I've tried to trace it to a certain app, but was unsuccessful in doing so.     Can someone perhaps help with some advice on this, on how to get rid of it? Which focal-length lens is usually used for portrait photography, and why? What focal length or range of focal lengths are usually used for portraits?   What is used by professionals? Why would one select a certain focal length? What are the advantages and disadvantages of different choices, and are there certain situations where an unusual choice might be better? When will data.SE get updated data? How to change XML Attribute How can I change an attribute of an element in an XML file, using C#? I've fitted my model and am trying to understand whether it's any good. 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Best,  Alari To an an external observer it appears that time has stopped for photon. But this relation is reflexive, so for an observer travelling with the photon it appears the universe has stopped everywhere.  Is this right?  Space also gets distorted parallel to the direction of motion, but not perpendicular to it.   Does this mean that for an observer travelling with a photon sees spacetime as a flat plane?  Note 1: I'm using language vividly not literally when I say a photon experiences space and time. Not that I'm against idealist or panpyschist interpretations of matter or energy come to that.  Note 2: Since it's been pointed out that an inertial frame can't be boosted into the frame of a photon and moreover there is no limiting behaviour here - no matter what frame you are boosted into, light will always appear to travel at c. 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