Does Super Mario physics work in reality?
Jumping in an elevator?
How restrict page for users logged? I have a website with login page that works normal. The problem is that once logged in, the user still has access to the login page form to enter, which should not happen.  I would like to know a wordpres plugin that redirects this user to another page when they access it after login. How to prove that limit doesn't exist using epsilon-delta definition? It is easy to prove the limit exists, all we have to show is there exists a relationship between $\delta$ and $\epsilon$. But how are we supposed to prove limit doesn't exists? The problem is when we are proving for a limit we already know what the limit is and with that, algebra is all that's needed.   Please show through an example (you may show that $\lim_{x\rightarrow0} \frac{1}{x}$ doesn't exist)  If possible please use the explanation scheme that is used by this answer Convergence of $\sum_{n=1}^\infty (-1)^n(\sqrt{n+1}-\sqrt n)$ Please suggest some hint to test the convergence of the following series $$\sum_{n=1}^\infty (-1)^n(\sqrt{n+1}-\sqrt n)$$ Trying to get my head around the commutator subgroup. This is an excercise from Artin's Algebra:  Let $C$ be the commutator subgroup of $G$. Prove that $G/C$ is abelian.  Here is what I've done:  Let $xC,yC \in G/C$ then $xyx^{-1}y^{-1}C = C$ since $xyx^{-1}y^{-1}$ is a commutator hence belongs to $C$. But then $xyC = yxC$ so $xC$ and $yC$ commute in $G/C$. This can be done for any elements, so $G/C$ is abelian.  This seems somewhat surprisingly short. Is that all there is to it?   Regards Is it possible to follow a user automatically? I am running a web site design service for local small business owner. I want avoid legal issues on the images I use. Usually, the images found on Flickr are forbidden for commercial use. Where would be a normal channel to get pictures for commercial use with minimal cost? How can I validate that the picture I used has no legal risk? I have never had this problem before. But after seeing some questions posted on ELU, I started to doubt. I have been through links1, pages of grammar books2, a lot of questions3 posted here and ELU. I now still can't seem to understand how the past perfect is exactly used. The references sometimes even contradict each other.  What I had understood so far was      The past perfect is not necessary if we are not 'going back' to the earlier past, and simply moving from one event to another.   but I then saw a lot of other 'rules' including      If the sequence is clear, the past perfect is not needed.   which is slightly different, less 'narrow' and can be applied in more situations than the first ruleA, and      The past perfect is optional only when talking about an action at a specific time.   This is confusing. Can anyone here clarify things out please?    A For example, for  Doing the survey [completed] -&gt; Showing the result      We showed the result of the survey we did.      If the second rule is applied, the sentence above is fine (the sequence is clear), but not if the first rule since we are not moving from any event to the next and possibly even going back.    1  and   2 Practical English Usage (2005) by Michael Swan, Collins Cobuild Student's Grammar (1991). Upper-Intermediate Cutting Edge.  3 including , , ,  etc. How do you run your own code alongside Tkinter's event loop? My little brother is just getting into programming, and for his Science Fair project, he's doing a simulation of a flock of birds in the sky. He's gotten most of his code written, and it works nicely, but the birds need to move every moment.  Tkinter, however, hogs the time for its own event loop, and so his code won't run. Doing root.mainloop() runs, runs, and keeps running, and the only thing it runs is the event handlers.  Is there a way to have his code run alongside the mainloop (without multithreading, it's confusing and this should be kept simple), and if so, what is it?  Right now, he came up with an ugly hack, tying his move() function to &lt;b1-motion&gt;, so that as long as he holds the button down and wiggles the mouse, it works. But there's got to be a better way. My computer boots to a black screen, what options do I have to fix it? I am trying to boot Ubuntu on my computer.  When I boot Ubuntu, it boots to a black screen.  How can I fix this? Table of Contents: I have a default Blender cylinder positioned upright atop a ground plane:    How can I rig the cylinder so that can be animated to wiggle/jitter (perhaps procedurally with noise f-curve modifiers on two of its rotation axis) without penetrating the floor?    A simple parent-child relationship as in the image above is sufficient to rotate (and translate) the cylinder on 1 axis in either a positive OR negative direction.   I'm looking for a setup that would allow me easily to rotate the cylinder on two or even three axis in both a positive and negative direction.  I imagine this would be possible with some drivers applied to the XYZ coordinates using trigonometric equations but the math escapes me. It might also be possible using a particular bone setup with the correct constraints but my attempts to find something that works so far have not succeeded.  Thanks for your assistance. How to pass parameters to an alias? For bash script, I can use "$@" to access arguments. What's the equivalent when I use an alias? Let $f$ be continuous on $ [a,b]$, differentiable on $ (a,b) $ and $ f(x) \neq 0 \forall x \in (a,b) $ Prove $ \exists c \in (a,b) $ such that What to do when witches appear early in the game? A long time ago I played an older version of Minecraft. Back then witches didn't spawn naturally, so you couldn't find them unless you found a hut. Now I'm playing again, but sometimes when I go down a cave I find one or two witches, and it's really hard to find them back.   So, what is the best you can do to kill witches, specially when two spawn at the same time and you don't have milk? Prove: $\lim\limits_{n \to \infty} \int_{0}^{\sqrt n}(1-\frac{x^2}{n})^ndx=\int_{0}^{\infty} e^{-x^2}dx$ I'd like your help with the following claim to prove:  $$\lim_{n \to \infty} \int_{0}^{\sqrt n}\left(1-\frac{x^2}{n}\right)^ndx=\int_{0}^{\infty} e^{-x^2}dx.$$  I think I should use the claim:     Let $a,b$ two real numbers and $\{f_n\}$ a sequence of continuous functions on $\left[a,b\right]$  which converges uniformly to $f$ on $[a,b]$. Then    $$\lim_{n\to\infty}\int_a^bf_n(t)dt=\int_a^bf(t)dt.$$   But for this, I must prove that $(1-\frac{x^2}{n})^n$ uniformly converges to $e^{-x^2}$.  How do I do that? One of the hardest and trickiest things to do is to prove this uniformly converges.. every function has its own way. I believe that the more examples I'll see the easiest it will be. Thanks again! wrapfig: frame around image and caption What happened to the “‑est” and “‑eth” verb suffixes in English? What happened to them, and how were they once used? Straining my mind to sound archaic, I came up with the following:     Dost thou thinkest thou can escape thy sins?   and     Bringeth me mine armor and favorite sword.   I’d like to use these suffixes intelligently, so my questions are: how are ‑est and ‑eth properly appellated in conjugations, and  when and why did they disappear? If I make a scene and then render it with BR or Cycles, am I allowed to use that image in a commercial project? Do I need to include any copyright notice or license? So, when I point a laser at a piece of wire (pointed at a specific angle), a circle of light appears on a wall behind it (see image below). I am trying to see why this happens and if there are any readings on this. Could anyone give some tips on what I should search for or any references?   ()  So this is a problem for a physics tournament, but I haven't tried it myself yet. However I have found a video depicting what I mean. Find Orthogonal complement How to use the Bevel node in 2.79b