How can I know all of the invertible elements? Is it just all of the numbers that are relatively prime to 30?
Can anyone show me how to find invertible elements in $\mathbb{Z}/m\mathbb{Z}$, $m$ is say $28$?  Also I'm not very clear about what it mean by 'invertible element in $\mathbb{Z}/m\mathbb{Z}$'
So uh i've got this problem with a penetrating object and another object that serves as something like a condom if you will    So what I want, is for the penetrating object to not deform while moving into this "rubber cylinder", while the rubber cylinder does deform and reshape itself to the outer form of the penetrating object. That is, if the pen. object is bigger than the entrance hole ofc.  Also, when the object leaves the "rubber cylinder" I want the outer edges to follow (mid object in picture) and then jump back (right object in picture)    Parenting the size and position of the "rubber cylinder"-entrance to the position of the penetrating object would work i guess, but I think it'd create problems when the pen. object enters from another angle (not perpendicular to the entrance). I just read another post where someone mentions Vertex Weight Proximity modifier in a combination with a cast modifier. Don't know if thats gonna work yet. Couldn't find the time to test it. How to check if installing a package will require a reboot? When electric dipole placed in non uniform electric field, what is the approach to calculate torque acting on it? Can it be zero? Is “are” a borrowed word? I read somewhere that English is the only language to have borrowed a form of its to be verb from another language. I want to say, if memory serves, that it was are that was borrowed from an early Scandinavian language. Is that so?  I know Old English had sind for one of their pronouns inflections of be, the same as in German.  But did it switch to are naturally from some other gentler evolution, or was it borrowed? I need a two word phrase to refer to a community of people (academia + non-academia) who come together to share/exchange their knowledge/ideas openly on topics of their interests/ specializations.  I would appreciate the use of small and easier/common words for the phrase. Single words are also acceptable. Feel free to throw out your creative ideas and newly invented phrases. Strange GET requests in logs I'm getting the following GET requests in my apache logs:  109.230.251.14 - - [29/Mar/2011:16:28:18 +0100] "GET http://209.191.92.114/config/pwtoken_get?login=jackmcphee232&amp;src=ygodgw&amp;passwd=e59e2240415e6f1aba3da72b8f189f4e&amp;challenge=9TbU_9yfZhKmzlHtK9X4OkQlesTH&amp;md5=1 HTTP/1.0" 404 1226 "-" "-"   Any idea what it could be and how is that possibly a get request? That IP address seems to point to Yahoo! I'm very confused. Increase partition size on which Ubuntu is installed? I have Ubuntu installed on a drive. The problem is it is running low on disk space. This is installed on vmware. I expanded the virtual drive and booted into ubuntu. But when I opened gparted(sudo gparted), the move/resize option is unavailable. This is the partition Ubuntu is installed on, but I need to resize it. Any ideas? I am comfortable using command line Padding trailing whitespaces in a string with another character I'd like to output hello world over 20 characters.  printf "%-20s :\n\n" 'hello world!!'  # Actual output hello world!!        :  # Wanted output hello world!!========:   However, I don't want to complete with spaces but with "=" instead. How do I do that? I have upgraded 14.04 to 16.04 . Now I am trying to open the gedit from terminal by passing the command:    sudo gedit /some/where/file.txt   but it is throwing an error stating that:    (gedit:2090): Gtk-WARNING : Calling Inhibit failed: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown:   The name org.gnome.SessionManager was not provided by any .service files**   However, it is opening the file. When I try to save any modification then it is showing this error after saving the file:    (gedit:2090): WARNING : Set document metadata failed: Setting attribute metadata::gedit-position not supported   I am not getting why this is happening in 16.04 only; it was not on 14.04. Definitionally, we have that  $$ \int_\gamma f\ \overline{dz} = \overline{\int_\gamma \overline{f}\ dz} $$  Now let $\int_\gamma f\ dz = w = x +yi$.  Question 1: Is it not the case that $\int_\gamma \overline{f}\ dz = \bar{w} = x - iy$?  Question 2:  Assuming that $\int_\gamma \overline{f}\ dz = \bar{w} = x - iy$, then is it not the case that  $$ \overline{\int_\gamma \overline{f}\ dz} = \overline{x - iy} = x+iy = \int_\gamma f\ dz? $$  Basically, I'm failing to see how $\overline{\int_\gamma \overline{f}\ dz}$ isn't just $\int_\gamma f\ dz$. Pgfplots with custom axis markers Assume you have a trigonometric function, say for simplicity sin(x). When plotting the function, how can one place the x-axis markers on 0, pi/2, pi, 3pi/2, 2pi, instead of the default numeric values that pgfplots uses? Best method for short time-series How to disable all caches in safari 11? I am using Safari to develop for a while. One thing I always liked is when you clear the cache, it really does, unlike other browsers I tried in the past. But in previous versions, specially when working in a code in a local testing server, just reloading the page will reload everything from disk. Now I have to use de shortcut command+alt+e to clear before reload or some new CSS won't load, even some http request will return old values. Just reloading the page won't guarantee to show me the last modifications.  I looked at preferences and develop menu but didn't find an option to just don't use any caches at all - the perfect option will be don't use caches when I have the web inspector opened, means I am developing.  Did I miss this option, or there is another way to disable all caches? How do you reopen a closed question? To reopen a closed question,  must agree that the question is suitable for the site and cast votes to reopen the question. But:  How does one actually vote to reopen? Is there a reputation level that you must have before you can see this function? Or do I just leave a comment along the lines of, &quot;I vote to reopen&quot;? What happens if someone with less than 3000 reputation leaves a comment that they wish to vote to reopen? How can one draw attention to their closed questions? Is it done via a posting new question? Or do you edit the closed question?   Related:  For more information, see &quot;&quot; in the . Prove This Inequality ${\pi \over 2} \le \sum_{n=0}^{\infty} {1 \over {1+n^2}} \le {\pi \over 2} + 1$ $${\pi \over 2} \le \sum_{n=0}^{\infty} {1 \over {1+n^2}} \le {\pi \over 2} + 1$$  I see I should use Riemann sum, and that $$\int_0^{\infty} {dx \over {1+x^2}} \le \sum_{n=0}^{\infty} {1 \over {1+n^2}}$$  But how do I explain this exactly, and how to get the other half of the inequality (with ${\pi \over 2} + 1$)? Should “two weeks vacation” be written “two weeks’ vacation” with a possessive apostrophe? I’ve always understood that the phrase two weeks usually turns into two weeks’ when used as a modifier as in   I’m giving my two weeks’ notice.  I get two weeks’ vacation. (“two weeks’ holiday” for Brits)   with an apostrophe on the word weeks’, indicating that the vacation “belongs” to the weeks.   One way to explain this is the phrase “two weeks of vacation” being contracted to “two weeks’ vacation” – the vacation is “of” the weeks; that is, it is possessed by them.  But I’ve seen a lot of people omit the apostrophe in casual writing, and thinking about it, it seems plausible that the noun vacation would be plainly modified by the adjectival phrase two weeks.  But on the other hand, shouldn’t adjectival phrases be hypenated, namely two-weeks vacation?  Yet that seems wrong, too: the hyphenate should be singular, two-week vacation (like two-tone shoes) because .   touches on this (and references a good ) but doesn’t explain why the plural must be possessive in this case.   suggests that two weeks might be adverbial rather than adjectival, and thus resists being used attributively. But that still doesn’t quite explain this particular muddle of pluralization, possession, and attribution.  Given all this, why should “two weeks vacation” be written “two weeks’ vacation” with a possessive apostrophe? Number of possible marriage arrangements if Marriage Condition is satisfied Suppose I have a set of $n$ boys and each subset of $1\leqslant k \leqslant n$ boys knows at least $k$ girls then this means that the set of boys $B$ satisfies the marriage condition.  I am doing an exercise from a Graph Theory book and it says we can show by induction on $n$ that the number of possible marriage arrangements is $\geqslant t!$ if every individual boy knows at least $t \leqslant n$ girls or there are $\geqslant t!/(t-n)!$ possible marriages if each individual boy knows at least $t&gt;n$ girls.   I am struggling to see how the induction hypothesis can be implemented to prove the $n+1$ case. When you swap from the $n$ to $n+1$ case the conditions change and I can't see the link between them.  Would anyone be able to point me in the right direction? How to draw a torus Is there an easy way to draw a contour image of torus below with tikz? Or for that matter with any other graphics package. MonoTouch.Dialog: How to set limit of number of characters for EntryElement Installed memory 4GB but only 1.93 GB is usable shows in system properties dialog? In my Intel Core i5 2.80 GHz CPU , DH55HC series Intel mother board machine installed with windows 7 64 bit  machine, when I right click my computer and see system properties I see that "Installed Memory(RAM): 4 GB(1.93 usable)".I have 2 x 2 GB DDR 3 RAM modules.  I have verified, * Two of RAM modules are working * Two of RAM slots in mother board are working   What are the cause(s) for this might be to look next ie: what settings in BIOS etc ?