Jacobian and changing coordinates proof
Wedge product and change of variables
Last upgrade crashes network manager (no internet connection, no applet) While upgrading today, something caused my wireless network manager to disappear. Not even connecting via wired connection.  This error is being shown by files:  **(nm-applet:2716): WARNING **: Could not initialize NMClient /org/freedesktop/NetworkManager: The name org.freedesktop.NetworkManager was not provided by any .service files   (nm-applet:2716): nm-applet-WARNING **: Error connecting to ModemManager: Error calling StartServiceByName for org.freedesktop.ModemManager1: GDBus.Error:org.freedesktop.DBus.Error.Spawn.ExecFailed: Cannot launch daemon, file not found or permissions invalid   (nm-applet:2716): nm-applet-WARNING **: Could not find ShellVersion property on org.gnome.Shell after 5 tries   (nm-applet:2716): nm-applet-WARNING **: Failed to register as an agent: (2) The name org.freedesktop.NetworkManager was not provided by any .service files    Is there a patch I can download through windows and send through to my ubuntu, or is it a case of having to reload everything? I tried running two versions back but still no internet access. What is currently the best way to get a favicon to display in all browsers that support Favicons? I'm reading through  for the , which contains this figure on page 16:    This is of course an instrumentation amplifier that apparently uses an inverting amplifier's output instead of a ground in the lower-right corner of the above figure, but what really perplexes me is the 100 k&Omega; resistors attached directly to the noninverting inputs of three of the four amps. I don't recall seeing an instrumentation amplifier circuit in books or application notes that have them, and all of the instrumentation amplifiers I've built using the three op-amp scheme works fine without them.  The datasheets specifies an input resistance of 1012 &Omega;, which is 10,000,000 times greater than 100 k&Omega;, so it doesn't seem to add anything to the already high-impedance JFET inputs. I thought perhaps it has something to do with input bias currents, but that's just me making a wild stab in the dark.  Curiously, figure 26 in the same datasheet (page 18) shows a two-op-amp version of an instrumentation amplifier without the 100 k&Omega; resistors at the noninverting op-amp inputs!  What's the purpose of the 100 k&Omega; resistors at the noninverting inputs in the above circuit? Am I missing something completely obvious? How long does the ubuntu installation take and what to do after it? How to write the Fibonacci Sequence? I need help with this:  If a is an element of $\mathbb Z_n$ and $\gcd(a,n) &gt; 1$ , then a is not invertible.   First you show that if $a$ is an element of $\mathbb Z_n$ and $\gcd(a,n)&gt;1$, then there  is an element $b$ of $\mathbb Z_n$ and ($b$ is not equal to the zero element) from which $ab = 0$.   The second part I cant get. i.e. show if $b$ is not the zero element  and $ab=0$ then $a$ is not invertible. Anyone know of a custom GPS ROM for Samsung Galaxy 5? Possible Duplicate:          I recently bought a Samsung Galaxy 5 (model number GT-I5500) and I'm new to the android world.   I'm not satisfied with the performance of the GPS on my cell phone so I thought it would be interesting to use a custom ROM to see if it improves a bit.   Anyone knows of a ROM that was tested in this model? Can I override the Javascript Function object to log all function calls? Unexpected output of xargs The statement below should print afc abc but it prints abc abc instead. I tried many times but every time same result Don't know why this happens could anyone explain and help me?  echo abc|xargs -i{} echo $(echo {}|sed 's/b/f/g') {} Inheriting constructors How to assign permanent drive letters to removable USB hard drives I have scripts that expect specific drive letters for hard drives. Windows sometimes assigns the different drive letters (e.g. I expected my Maxtor drive to be E:, but it's now F:, therefore my scripts will fail), depending on the order of how the drives are plugged into my laptop.  In Windows 7, how do I assign a permanent drive letter to a drive? What color codes can I use in my PS1 prompt? I used several colors in my PS1 prompt such as   \033]01;31\] # pink \033]00m\]   # white \033]01;36\] # bold green \033]02;36\] # green \033]01;34\] # blue \033]01;33\] # bold yellow   Where can I find a list of the color codes I can use?  I looked at  but it didn't answer my question about a list of the actual codes.  It would be nice if there was a more readable form also.  See also Short brandable domain vs. long keyword domain I need a counsel about my websites' domain.  Let's say I have just bought two domains: xyz.com and xyzphotography.com.  As we can see, the first one is shorter but way less meaningful than the second one. The second one contains a photography keyword but it's longer.  I have only one website which is my photography portfolio. Can you advise me how to set those domains to make it all as SEO-friendly as possible? Which one should be the main one, does the rest should work on their own or have some kind of SEO-friendly redirect to the main domain? How to cd into a directory with this name "-2" (starting with the hyphen)? I have a directory named:  -2   I want to cd into it but the cd complains:  bash: cd: -2: invalid option   With no success, I've tried:  cd "-2" cd '-2' cd \-2   Any solution?  Edit: no file browsers like mc, etc. available on the server. MCP4131: How to know what value resistors to use on the multiplexed SPI IO? There are two aspects here. The first question is related to R1 below:    The datasheet says: "R1 must be sized to ensure VIL and VIH of the devices are met" but gives no formula. So first question:  (1) How does one determine value of R1?  The datasheet gives maximum SPI SCK frequency for this device as 10MHz for 5V supply as given in Tables 1-1 and 1-2. However, for the read operation on the device where the SDI/SDO are multiplexed, the idea is different because:    The point 2 under the Table above says that the max SCK can be increased by using a pull up resistor. About these things I am wondering the following:  (2) Why is max SCK frequency lower for multiplexed SDI/SDO read operation only? (3) If I connect a pull-up resistor it will certainly form a voltage divider with the R1 in the first picture. How do I determine the value of both of these resistors then?  Finally, since the Table 1-1 and 1-2 give SCK Input Frequency for voltage 1.8V to 2.7V as 1MHz rather than 10MHz which applies to 2.7V to 5.5V.   (4) Why is the max SCK lowered at lower supply voltage? Does a creature with Lifelink provide lifegain equal to its power, or the defender's toughness? Font corruption: lines through characters I have a problem where a one-pixel high white line is displayed through certain letters of text. Almost always only a single character type is affected at once, and only in one font size (though that size can change over time). Most of the time things are fine, but this happens several times a day. It happens frequently in Firefox, but system dialogs, menus, etc. can also be affected. It's been happening ever since I upgraded to 10.10. Only restarting seems to fix it.  Two examples (in the first, only the larger "r" is corrupted):     Any help would be appreciated, thanks.  Edit: I've since noticed that I can (sometimes) make the fonts appear correctly by zooming in/out all the way and returning to the default in Firefox (one or two steps, then going back, does nothing) seems to make the problem go away temporarily.  Edit 2: I figure it's worth noting that the solution below doesn't fully work for me any longer (I'm now using Ubuntu 11.10). It does significantly reduce the frequency of this problem occurring.  Edit 3: Still around in 12.04. The fix provided by Vanni works perfectly now for me, but apparently doesn't for some.  Edit 4: This seems to be an xorg problem, with Vanni's answer fixing it for many Intel video cards. I've had this occasionally happen with AMD graphics cards in 13.10 and 14.04, but very rarely (only two or three times). Do I leave a revised question closed even though it falls out of scope for a different reason than the original closure reason? Give $a, b. c$ be the lengths of a triangle and $a+ b+ c= 3$. Prove that: $$\frac{a}{b}+ \frac{b}{c}+ \frac{c}{a}\geq  \frac{1}{a}+ \frac{1}{b}+ \frac{1}{c}$$ My try  We have England MO inequality: $$\left ( \frac{a}{b}+ \frac{b}{c}+ \frac{c}{a} \right )^{2}\geq  \left ( a+ b+ c \right )\left ( \frac{1}{a}+ \frac{1}{b}+ \frac{1}{c} \right )$$  and $$\frac{a}{b}+ \frac{b}{c}+ \frac{c}{a} \geq  3=  a+ b+ c$$  But it cannot be used to prove the above inequality and how to use triangle inequality in this inequality. I need the help. Thanks! Adding many more neutrons to a nucleus decreases stability? If you take any large nucleus and add protons to it, the electrostatic repulsion between them will make the nucleus more unstable, because the electrostatic force between them is more repulsive at a greater distance than the strong force is attractive  So how come if you add more neutrons, which don't have a charge and so there is no electrostatic force, the nucleus still becomes more unstable?  Also why aren't there groups of neutrons bound together, so purely neutron nuclei (because they are neutral, I'm guessing they couldn't form atoms, because of the electrons needed for an atom)