*E: The repository 'http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu focal Release' does not have a Release file.  N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.
When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do?
I find that at the end of a long day, I sometimes have a large number of programs running. All which I will need to use tomorrow. Normally, this isn't an issue, I can simply lock the machine and come back tomorrow. My problem arrises when windows update launches in the middle of the night and force restarts my computer. That in turns closes all my open software. I of course save everything regularly so I don't loose anything, but I waste time reopening all of those resources whenever there is a restart.   [EDIT]  I should clarify that I still want to be able to restart my computer when an update comes down. Preventing the restart only delays the problem until later. I should have been more specific in that I want to be able to recover my working environment after a restart for any reason. Things like scheduled maintence, power loss, updates, and software installs.  [EDIT]  I can't simply have them setup to launch at startup becasuse those files change from week to week. So I need something that monitors what I have open, and gives me the option to "recover" those software sessions when I log back in.  Anyone have any suggestions on what I can do? I'd even be willing to purchase software to do this for me if that is the only option.  Thanks double r = 11.631; double theta = 21.4;   In the debugger, these are shown as 11.631000000000000 and 21.399999618530273.  How can I avoid this? Why is a boolean value in JTable showing as true/false instead of a checkbox? Complex numbers - Exponential numbers - Proof Let $z$ be a complex number, and let $n$ be a positive integer such that $z^n = (z + 1)^n = 1$. Prove that $n$ is divisible by 6.  For this problem I am stumped...how should I begin? Also there's a hint for it:  From $z^n = 1$, prove that $|z| = 1$. What does the equation $(z + 1)^n = 1$ tell you? What do the resulting equations tell you about $z$?  Could someone give me a hint on where to begin? thanks in advance I've been wondering what makes the  such an important model. What I came up with:   It is a (relatively) simple system, making it a perfect example for physics students to learn principles of classical and quantum mechanics. The harmonic oscillator potential can be used as a model to approximate many physical phenomena quite well.   The first point is sort of meaningless though, I think the real reason is my second point. I'm looking for some materials to read about the different applications of the HO in different areas of physics. $\nabla U=0 \implies U=\mathrm{constant}$ only if $U$ is defined on a connected set? Prove inequality using Schwarz's Lemma Compile error: package javax.servlet does not exist Seeing close-vote details if I've already voted If I've already voted to close a question, it would still be nice to see the details of others' votes — the suggested migration if it's being marked as off topic, or the suggested duplicate if it's being marked as an exact duplicate, for instance. Instead, I only see "You have already voted to close this question" and the overall category. How can an uneducated but rational person differentiate between science and religion? I recently found myself unable to respond to the statement "But the big bang theory is just another creation myth!" during a science vs. religion argument. I found it very difficult to explain the difference between the big bang theory and creation myths without going through a crash course in Newtonian and then Relativistic mechanics.   This had me thinking of the following scenario: Consider a person who for various reasons never got a formal education beyond basic reading and writing. He/She doesn't know any science or math, and was never exposed to any scientific reasoning and experiments. She/He is however an open minded, level headed, and rational person (I've met more than one such person myself).   How would such a person differentiate science from religion? As far as he/she is concerned science has the exact same structure as religion:    A hard to understand scripture: Science treatises and journal papers.  An ordained clergy with a high entry barrier: Doctors, professors, scientists, etc... Seemingly arbitrary injunctions against certain behaviors: "Don't smoke", "Don't pollute",.... Various metaphysical (from his/her perspective) claims about the world around us: The big bang, other galaxies, blackholes, quarks,... Organizations which control and oversee doctrine: The FDA, The NIH, The NFS,...   From his/her perspective, all of these characteristics are no different than the way organized religion presents itself as being the source of truths about the world.   In particular if such a person were to heed the advice of the :         Do not go upon what has been acquired by repeated hearing (anussava),   nor upon tradition (paramparā),   nor upon rumor (itikirā),   nor upon what is in a scripture (piṭaka-sampadāna)   nor upon surmise (takka-hetu),   nor upon an axiom (naya-hetu),   nor upon specious reasoning (ākāra-parivitakka),   nor upon a bias towards a notion that has been pondered over (diṭṭhi-nijjhān-akkh-antiyā),   nor upon another's seeming ability (bhabba-rūpatāya),   nor upon the consideration, The monk is our teacher (samaṇo no garū) Kalamas, when you yourselves know: "These things are good; these   things are not blamable; these things are praised by the wise;   undertaken and observed, these things lead to benefit and happiness,"   enter on and abide in them.'      Following the Buddha's advice (ironically himself a religious figure), such a rational but uneducated person would have just as much reason to doubt the various results of scientists as to doubt the dogmas of organized religion.    How would it be possible for such a person to distinguish scientific facts from religious dogma?  How can we convince such a person of the validity of ideas like those of modern cosmology or evolutionary biology, without first having to teach them enough biology and physics to understand those concepts? Why Do Glueballs Have Mass, When Individual Gluons Are Massless? How do I change my update server in Ubuntu 18.04? I'm trying to update my system using apt-get, but it's giving me this error  Err http://bd.archive.ubuntu.com raring Release.gpg          Could not connect to bd.archive.ubuntu.com:80 (116.193.170.18), connection timed out Err http://bd.archive.ubuntu.com raring-updates Release.gpg   Unable to connect to bd.archive.ubuntu.com:http: Err http://bd.archive.ubuntu.com raring-backports Release.gpg   Unable to connect to bd.archive.ubuntu.com:http: Reading package lists... Done W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/raring/Release.gpg  Could not connect to bd.archive.ubuntu.com:80 (116.193.170.18), connection timed out W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/raring-updates/Release.gpg  Unable to connect to bd.archive.ubuntu.com:http: W: Failed to fetch http://bd.archive.ubuntu.com/ubuntu/dists/raring-backports/Release.gpg  Unable to connect to bd.archive.ubuntu.com:http: W: Some index files failed to download. They have been ignored, or old ones used instead.   I am not a Ubuntu master but I can understand this is not a computer error. Any clues on how to fix it? Prove that $\sin(\theta) + \sin(\theta+2\pi/3) + \sin(\theta+4\pi/3) = 0 $ for any angle $\theta$.   This came up in the context of electricity:  It is common in electrical power engineering to use three-phase circuits with sinusoidal currents out of phase with each other by 120 degrees. The benefit of this is that the currents sum to zero at the neutral point meaning less copper is required for the system.    However, while I know that the three phasors always sum to zero, and can see visually, as in the figure that this is true at every point, how can this be shown more formally, or algebraically? Finding determinant of matrix without expanding show that determinant $$\left|\matrix{ x^2+L  &amp;  xy   &amp;   xz \\ xy   &amp;    y^2+L &amp;   yz \\ xz   &amp;    yz   &amp;   z^2+L \\ }\right| =  L^2(x^2+y^2+z^2+L)$$  without expanding by using the appropriate properties of determinant.  All i can do is LHS  $$x^2y^2z^2\left|\matrix{ 1+L/x^2  &amp; 1  &amp;   1 \\ 1   &amp;   1+L/y^2 &amp;   1 \\ 1  &amp;    1   &amp;   1+L/z^2 \\ }\right|$$ Crash adding comment The SE iOS app crashes when adding comments to certain posts.  It was discovered to be if the "Add an Answer" button was visible, not just responding to a deleted comment.  Edited to match answer. Previous steps were not the only use case, and this error keeps getting re-reported in different ways. How can I tell what RAM will fit my computer? If I want to add more RAM to my computer, how can I buy something compatible? What kinds are there? How do I determine which kind my computer will accept and how much I can add? Interchanging the order of differentiation and summation A cashier wants to work five days a week, but he wants to have at least one of the Saturday and Sunday off.  In how many ways can he choose the days he will work?  So, in this case, what should I count first?  How do I start?  I know how to solve this if the cashier doesn't want a weekend off, but what do I do if the cashier do?  Thanks! Why is it so hard to do this in Java? If you want to have any kind of module system you need to be able to load JAR files dynamically. I'm told there's a way of doing it by writing your own ClassLoader, but that's a lot of work for something that should (in my mind at least) be as easy as calling a method with a JAR file as its argument.  Any suggestions for simple code that does this?