Is this wiring safe The wall box is from the mid-1950's and my multimeter shows that it is grounded. There are a solid 120 volts when testing between live and ground. I noticed a bare copper wire coming from the cloth wiring in the back tied to a screw connected to the box. I looked around for usable screw holes in the box to screw a ground screw into but they were all way too large. Does this look okay? I get good continuity here between the green insulated copper ground wire I added and the rest of the box.  The green wire will go to the grounding screw on the outlet.
Is this box bonded properly to the ground? The receptacle is from the mid-1950's and my multimeter shows that it is grounded. There are a solid 120 volts when testing between live and ground. I noticed a bare copper wire coming from the cloth wiring in the back tied to a screw connected to the box. I looked around for usable screw holes in the box to screw a ground screw into but they were all way too large. Does this look okay? I get good continuity here between the green insulated copper ground wire I added and the rest of the box.  The green wire goes to the ground screw on the new outlet in this case.
As I have heard people did not trust Euler when he first discovered the formula (solution of the ) $$\zeta(2)=\sum_{k=1}^\infty \frac{1}{k^2}=\frac{\pi^2}{6}.$$ However, Euler was Euler and he gave other proofs.   I believe many of you know some nice proofs of this, can you please share it with us? Word/phrase for the activity of hiding mistakes What word/phrase can I use to describe the activity of hiding a stupid mistake/incident, such as quickly cleaning up tea spilled by accident before anyone could notice? I can't download apps from the Play Store on my Android device (maybe due to a network issue), so I'm wondering how could I download the APK file of an app on my PC from ? An equality involving the mean value property I am trying to establish that  $$\frac2{\pi}\int_0^{2\pi} f(e^{i\theta})\cos^2\left(\frac{\theta}{2}\right)\;\mathrm d\theta=2f(0)+f^\prime(0)$$  for $f$ analytic on $|z| &lt; R,\; R &gt; 1$  I think I am making a mistake somewhere, please point it out to me.Here's what I've done unsing the mean value property and Cauchy's integral formula:  $$2f(0)+f&#39;(0)=2(\frac1{2\pi}\int_0^{2\pi} f(e^{i\theta})d\theta + \frac1{2\pi i}\int_0^{2\pi}\frac{f(e^{i\theta})ie^{i\theta}}{e^{i2\theta}}=\frac{1}{\pi}\int_0^{2\pi} f(e^{i\theta})d\theta\frac1{2\pi}\int_0^{2\pi}\frac{f(e^{i\theta})}{e^{i\theta}}\quad\text{(1)}$$  But when I develop the expression $\frac2{\pi}\int_0^{2\pi} f(e^{i\theta})\cos^2(\frac{\theta}{2}) d\theta$ I get:  $$\frac1{\pi}\int_0^{2\pi} f(e^{i\theta})d\theta+\frac1{2\pi}\int_0^{2\pi}f(e^{i\theta})[{e^{i\theta}}+e^{i-\theta}]d\theta \quad\text{(2)}$$  The second integral in (1) differs from the second integral in (2). Thanks. Trying to find a story about an unborn telepathic baby who can save a spaceship from doom Im using a program called Daisy Disk to see what is taking up space in my Mac and I find that the /cores directory is taking up 77gb.   Is that a problem? Can I get rid of it to regain the space? Classical car collision I have a very confusing discussion with a friend of mine.  2 cars ($car_a$ and $car_b$) of the same mass $m$ are on a collision course. Both cars travel at $50_\frac{km}{h}$ towards each other.  They collide. Ignoring any shreds and collateral damage, what is the speed of collision that the driver of $car_a$ felt?  What I mean is, if $car_a$ were to be driven into an infinite mass wall, what would the velocity be to replicate the damage caused by the initial collision? How can I run a command after boot? I would like to run the simple shell command echo 1 &gt; /proc/sys/kernel/sysrq at each boot, to enable the sysrq keys. When in boot should this be done, and where should I put a script to do it? Bold row in table aligned with dcolumn Should we use wheatstone bridges nowadays? For measuring strain gauges, the Wheatstone bridge is the historical choice.  In a quarter Wheatstone brigde (\$350 \Omega \$ typically (?)), with a high input impedance amplifier, and some bridge power voltage \$V\$, the ratio between the bridge output voltage w.r.t. any resistor is 1/4, which is the same ratio in a voltage divider between the output voltage w.r.t. any resistor, compared with a stable voltage reference of \$V/2\$.    A voltage divider with a voltage reference would have a voltage noise of about 35.16 nV/rtHz (from a voltage reference of 35 nV/rtHz plus two resistors), and the Wheatstone bridge a voltage noise of 4.86 nV/rtHz (from four resistors), which should be enough (?) for most ADC systems (i.e. for 24 bit, 0-5V range: 300nV resolution).  And a voltage reference (\$0.02\%\$ initial error, \$2 \ ppm/C^\circ\$, ), would be more stable and precise (?) about \$4\ ppm/C^\circ\$, than a precision resistor (\$0.005\%\$ error, \$2 \ ppm/C^\circ \$, ), about \$8 \ ppm/C^\circ\$.  Hence, why bother using Wheatstone bridges? Why does this Excel file keep asking to save? There is an alignment issue in the stackexchange.com search page .  The bottom bar is missing in the search input box.  Sample URL:   Screen shot for reference:    Firefox version: 54.0b8 (32-bit) OS Version: Windows 10 Pro  Also happens with Chrome latest version. How do I remove the Unity launcher? How can we remove the launcher that come with Unity on this new Ubuntu version ? Does $\int_{0}^{\infty}\frac{dx}{1+(x\sin5x)^2}$ converge? I would like your help with deciding whether the following integral converges or not:  $$\int_{0}^{\infty}\frac{dx}{1+(x\sin5x)^2}.$$  I tried to compare it to other functions and to change the variables, but it didn't work for me.  Thanks a lot! How to enable MySQL client auto re-connect with MySQLdb? I came across PHP way of doing the trick:  my_bool reconnect = 1; mysql_options(&amp;mysql, MYSQL_OPT_RECONNECT, &amp;reconnect);   but no luck with MySQLdb (python-mysql).  Can anybody please give a clue? Thanks. gedit "cannot open display" , on remote computer , using ssh - Ubuntu 12.04 Why does $x$ divided by zero not equal $x$? Why does $x$ divided by zero not equal $x$? After all, $x$ is not being divided by anything. Do I need an airport transit visa for Dublin, Ireland en route to the UK? I am Haitian, and traveling with a Haitian passport. I have to go to London with a work permit (tier 2 visa) on the 29th of July but I have 2 hour transit in Dublin.  Do I need a transit visa? Can I get it at the airport?  I also have a valid US visa. folder content doesn't get refreshed automatically in ubuntu 14.04 Let $X, Y$ be an exponentially distributed random variables with parameters $a, b$. Then $X$ has pdf:    $$f_X(x) =\begin{cases} a e^{-a x},&amp; x\geq 0\\ 0,&amp; \text{otherwise}.\end{cases}$$ Suppose $X$ and $Y$ independent. Show that $$\mathbb P(X&gt;Y) = \frac{b}{a+b}.$$   Now I thought the following: $$f(x,y) = f_X(x)\ f_Y(y) = abe^{-ax -by},\qquad\text{for } x,y &gt; 0.$$ And then $$\mathbb P(X&gt;Y) = \int_0^\infty \int_0^x a b e^{-ax -by}\,dydx$$ However, if I solve this (manually or using Wolframalpha), I can't seem to end up with $\frac{b}{a+b}$. Any ideas?