By default Libre/Open Office will not allow you to delete form fields in Microsoft .doc or .docx files. When you try to get rid of form fields, you will get an error message like one below.
Continue reading LibreOffice: Readonly content cannot be changed
If you have ever wondered how usable Android phone is without having Google account, most probably you have already discovered the ugly truth – Android phone is a trap. There is no visible chance to have a smartphone (with apps and so on) without having Gmail account. Majority of Alternative Markets, like GetJar, are available only from Google Play.
Sadly, most developers publish their Android apps only in Play store. You can’t download or buy their apps from developers websites. You can’t even download APK files to your computer using fake gmail account. And when you give up and enter your Gmail credentials in your Android phone there is no turning back – you can’t just disconnect your phone from Google.
In this article I share my experience and guidelines on using Android phone avoiding Google Play store.
If your website is under construction, you can simply edit .htaccess file to disallow visits to your website.
Here is the code :
<Limit GET POST PUT>
order deny,allow
deny from all
allow from 12.345.67.890
</Limit>
allow from 12.345.67.890 command allows access to your server only from 12.345.67.890 IP address.
You can allow more IP’s to access your website :
<Limit GET POST PUT>
order deny,allow
deny from all
allow from 12.345.67.890
allow from 890.67.345.12
</Limit>
This practice is good in case you are modifying your website (performing a new joomla installation) and don’t want others to see the process.
Original source: http://htaccessfile.com/htaccess-allow-ip-addresses
Add RPM fusion repository
Download RPM fusion package from http://rpmfusion.org/Configuration
Add it
yum localinstall –nogpgcheck rpmfusion-free-release-19.noarch.rpm
yum localinstall –nogpgcheck rpmfusion-nonfree-release-19.noarch.rpm
Install Flash plugin for 64bit systems
yum install http://linuxdownload.adobe.com/adobe-release/adobe-release-x86_64-1.0-1.noarch.rpm -y
Read more about playing flash here.
Install applications according to your needs
yum install gnome-tweak-tool
yum install gimp
yum install inkscape
yum install thunderbird
yum install vlc
yum install VirtualBox
yum install filezilla
yum install bluefish
yum install python-openoffice
Fix AltTab behavior so it switches windows only on the active workspace
https://extensions.gnome.org/extension/15/alternatetab/ (does not group windows by application)
https://extensions.gnome.org/extension/310/alt-tab-workspace/ (groups windows by application)
Fix keyboard shortcuts for static workspaces
yum install dconf-editor
In dconf-editor go to org → gnome → desktop → wm → keybindings
You have to disable dynamic workspaces prior to this.
Enable DVD playback
rpm -Uvh http://rpm.livna.org/livna-release.rpm
yum -y install gstreamer-plugins-bad gstreamer-plugins-bad-free-extras gstreamer-plugins-bad-nonfree gstreamer-plugins-ugly gstreamer-ffmpeg ffmpeg mencoder ffmpeg2theora mplayer libdvdcss
yum -y install gstreamer1-libav gstreamer1-plugins-bad-free-extras gstreamer1-plugins-bad-freeworld gstreamer1-plugins-base-tools gstreamer1-plugins-good-extras gstreamer1-plugins-ugly gstreamer1-plugins-bad-free gstreamer1-plugins-good gstreamer1-plugins-base gstreamer1
yum -y install libdvdread libdvdnav lsdvd libdvdcss libdvdcss2
Chromium web browser
yum-config-manager --add-repo=http://repos.fedorapeople.org/repos/spot/chromium-stable/fedora-chromium-stable.repo
yum install chromium -y
Read more about Chromium web browser here.
With gnome-shell, you’ll need to create a .desktop file in ‘~/.local/share/applications/’ which will then allow you to add the application to the gnome-shell dash.
Continue reading How to add manual entries to Gnome Shell Launcher
Punktu A, B, C koordinātes ir zināmas no mērījumiem– tās ir attiecīgi x1, y1, x2, y2, x3, y3. Riņķa līnijas centrs ir punkts O, kura koordinātes x, y nav zināmas. Izmantojot Pitagora teorēmu, varam uzrakstīt 3 vienādojumu sistēmu, kas saista zināmās koordinātes ar x, y un meklējamo rādiusu r:
(x – x1)2 + (y – y1)2 = r2
(x – x2)2 + (y – y2)2 = r2
(x – x3)2 + (y – y3)2 = r2
Vienādojumu sistēmu var risināt, piemēram, no pirmā vienādojuma atņemot otro – iegūsim sakarību y(x), ko tālāk var ievietot trešajā vienādojumā. Tomēr izteiksmes ātri kļūst pārāk garas aprēķiniem “ar roku”. Izmantosim vienu no brīvi pieejamajām datoralgebras programmām – Maxima (versija 5.27.0, http://maxima.sourceforge.net).
Vienādojumu sistēma kā uzdevums programmai Maxima izskatās šādi:
eq_1: (x - x1)^2 + (y - y1)^2 = r^2$
eq_2: (x - x2)^2 + (y - y2)^2 = r^2$
eq_3: (x - x3)^2 + (y - y3)^2 = r^2$
solve ([eq_1, eq_2, eq_3],[x,y,r]);
Rādiusam r programma sniedz risinājumu:
r=(sqrt(y2^2*y3^4-2*y1*y2*y3^4+y1^2*y3^4+x2^2*y3^4-2*x1*x2*y3^4+x1^2*
y3^4-2*y2^3*y3^3+2*y1*y2^2*y3^3+2*y1^2*y2*y3^3-2*x2^2*y2*y3^3+4*x1*x2*y2*y3^3-2*x1^2*y2*y3^3-2*y1^3*y3^3-2*x2^2*y1*y3^3+4*x1*x2*y1*y3^3-2*x1^2*y1*y3^3+
y2^4*y3^2+2*y1*y2^3*y3^2-6*y1^2*y2^2*y3^2+2*x3^2*y2^2*y3^2-2*x2*x3*y2^2*y3^2-2*x1*x3*y2^2*y3^2+2*x2^2*y2^2*y3^2-2*x1*x2*y2^2*y3^2+2*x1^2*y2^2*y3^2+2*y1^3*y2*
y3^2-4*x3^2*y1*y2*y3^2+4*x2*x3*y1*y2*y3^2+4*x1*x3*y1*y2*y3^2+2*x2^2*y1*y2*y3^2-8*x1*x2*y1*y2*y3^2+2*x1^2*y1*y2*y3^2+y1^4*y3^2+2*x3^2*y1^2*y3^2-2*x2*x3*
y1^2*y3^2-2*x1*x3*y1^2*y3^2+2*x2^2*y1^2*y3^2-2*x1*x2*y1^2*y3^2+2*x1^2*y1^2*y3^2+2*x2^2*x3^2*y3^2-4*x1*x2*x3^2*y3^2+2*x1^2*x3^2*y3^2-2*x2^3*x3*y3^2+2*x1*x2^2*x3
*y3^2+2*x1^2*x2*x3*y3^2-2*x1^3*x3*y3^2+x2^4*y3^2-2*x1*x2^3*y3^2+2*x1^2*x2^2*y3^2-2*x1^3*x2*y3^2+x1^4*y3^2-2*y1*y2^4*y3+2*y1^2*y2^3*y3-2*x3^2*y2^3*y3+4*x1*
x3*y2^3*y3-2*x1^2*y2^3*y3+2*y1^3*y2^2*y3+2*x3^2*y1*y2^2*y3+4*x2*x3*y1*y2^2*y3-8*x1*x3*y1*y2^2*y3-4*x2^2*y1*y2^2*y3+4*x1*x2*y1*y2^2*y3+2*x1^2*y1*y2^2*y3
-2*y1^4*y2*y3+2*x3^2*y1^2*y2*y3-8*x2*x3*y1^2*y2*y3+4*x1*x3*y1^2*y2*y3+2*x2^2*y1^2*y2*y3+4*x1*x2*y1^2*y2*y3-4*x1^2*y1^2*y2*y3-2*x2^2*x3^2*y2*y3+4*x1*
x2*x3^2*y2*y3-2*x1^2*x3^2*y2*y3+4*x1*x2^2*x3*y2*y3-8*x1^2*x2*x3*y2*y3+4*x1^3*x3*y2*y3-2*x1^2*x2^2*y2*y3+4*x1^3*x2*y2*y3-2*x1^4*y2*y3-2*x3^2*y1^3*y3+4
*x2*x3*y1^3*y3-2*x2^2*y1^3*y3-2*x2^2*x3^2*y1*y3+4*x1*x2*x3^2*y1*y3-2*x1^2*x3^2*y1*y3+4*x2^3*x3*y1*y3-8*x1*x2^2*x3*y1*y3+4*x1^2*x2*x3*y1*y3-2*x2^4*y1*
y3+4*x1*x2^3*y1*y3-2*x1^2*x2^2*y1*y3+y1^2*y2^4+x3^2*y2^4-2*x1*x3*y2^4+x1^2*y2^4-2*y1^3*y2^3-2*x3^2*y1*y2^3+4*x1*x3*y1*y2^3-2*x1^2*y1*y2^3+y1^4*y2^2+2*
x3^2*y1^2*y2^2-2*x2*x3*y1^2*y2^2-2*x1*x3*y1^2*y2^2+2*x2^2*y1^2*y2^2-2*x1*x2*y1^2*y2^2+2*x1^2*y1^2*y2^2+x3^4*y2^2-2*x2*x3^3*y2^2-2*x1*x3^3*y2^2+2*x2^2*x3^2*y2^2
+2*x1*x2*x3^2*y2^2+2*x1^2*x3^2*y2^2-4*x1*x2^2*x3*y2^2+2*x1^2*x2*x3*y2^2-2*x1^3*x3*y2^2+2*x1^2*x2^2*y2^2-2*x1^3*x2*y2^2+x1^4*y2^2-2*x3^2*y1^3*y2+4*x2*x3*y1^3*
y2-2*x2^2*y1^3*y2-2*x3^4*y1*y2+4*x2*x3^3*y1*y2+4*x1*x3^3*y1*y2-2*x2^2*x3^2*y1*y2-8*x1*x2*x3^2*y1*y2-2*x1^2*x3^2*y1*y2+4*x1*x2^2*x3*y1*y2+4*x1^2*x2*x3
*y1*y2-2*x1^2*x2^2*y1*y2+x3^2*y1^4-2*x2*x3*y1^4+x2^2*y1^4+x3^4*y1^2-2*x2*x3^3*y1^2-2*x1*x3^3*y1^2+2*x2^2*x3^2*y1^2+2*x1*x2*x3^2*y1^2+2*x1^2*x3^2*y1^2-2*x2^3*
x3*y1^2+2*x1*x2^2*x3*y1^2-4*x1^2*x2*x3*y1^2+x2^4*y1^2-2*x1*x2^3*y1^2+2*x1^2*x2^2*y1^2+x2^2*x3^4-2*x1*x2*x3^4+x1^2*x3^4-2*x2^3*x3^3+2*x1*x2^2*x3^3+2*x1^2*x2*
x3^3-2*x1^3*x3^3+x2^4*x3^2+2*x1*x2^3*x3^2-6*x1^2*x2^2*x3^2+2*x1^3*x2*x3^2+x1^4*x3^2-2*x1*x2^4*x3+2*x1^2*x2^3*x3+2*x1^3*x2^2*x3-2*x1^4*x2*x3+x1^2*x2^4-2*x1^3
*x2^3+x1^4*x2^2))/((2*x2-2*x1)*y3+(2*x1-2*x3)*y2+(2*x3-2*x2)*y1)
Redzams, ka meklēto rādiusu r var aprēķināt no 6 zināmajiem skaitļiem – koordinātēm x1, y1, x2, y2, x3, y3 – izmantojot tikai vienkāršas aritmētiskās darbības.
Atrisinājumā ir dalīšana ar izteiksmi
(2*x2-2*x1)*y3+(2*x1-2*x3)*y2+(2*x3-2*x2)*y1
Šīs izteiksmes vērtība kļūst vienāda ar 0, ja visi trīs punkti A, B un C atrodas uz vienas taisnes – to var iztēloties kā pagriezienu, kura rādiuss ir bezgalīgi liels.
Varam pārbaudīt izteiksmes pareizību ar vienkāršu piemēru programmā Maxima:
x1: 1;
y1: 0;
x2: 0;
y2: 1;
x3: -1;
y3: 0;
r: (sqrt(y2^2*y3^4-2*y1*y2*y3^4+y1^2*y3^4+x2^2*y3^4-2*x1*x2*y3^4+x1^2*
y3^4-2*y2^3*y3^3+2*y1*y2^2*y3^3+2*y1^2*y2*y3^3-2*x2^2*y2*y3^3+4*x1*x2*y2*y3^3-2*x1^2*y2*y3^3-2*y1^3*y3^3-2*x2^2*y1*y3^3+4*x1*x2*y1*y3^3-2*x1^2*y1*y3^3+
y2^4*y3^2+2*y1*y2^3*y3^2-6*y1^2*y2^2*y3^2+2*x3^2*y2^2*y3^2-2*x2*x3*y2^2*y3^2-2*x1*x3*y2^2*y3^2+2*x2^2*y2^2*y3^2-2*x1*x2*y2^2*y3^2+2*x1^2*y2^2*y3^2+2*y1^3*y2*
y3^2-4*x3^2*y1*y2*y3^2+4*x2*x3*y1*y2*y3^2+4*x1*x3*y1*y2*y3^2+2*x2^2*y1*y2*y3^2-8*x1*x2*y1*y2*y3^2+2*x1^2*y1*y2*y3^2+y1^4*y3^2+2*x3^2*y1^2*y3^2-2*x2*x3*
y1^2*y3^2-2*x1*x3*y1^2*y3^2+2*x2^2*y1^2*y3^2-2*x1*x2*y1^2*y3^2+2*x1^2*y1^2*y3^2+2*x2^2*x3^2*y3^2-4*x1*x2*x3^2*y3^2+2*x1^2*x3^2*y3^2-2*x2^3*x3*y3^2+2*x1*x2^2*x3
*y3^2+2*x1^2*x2*x3*y3^2-2*x1^3*x3*y3^2+x2^4*y3^2-2*x1*x2^3*y3^2+2*x1^2*x2^2*y3^2-2*x1^3*x2*y3^2+x1^4*y3^2-2*y1*y2^4*y3+2*y1^2*y2^3*y3-2*x3^2*y2^3*y3+4*x1*
x3*y2^3*y3-2*x1^2*y2^3*y3+2*y1^3*y2^2*y3+2*x3^2*y1*y2^2*y3+4*x2*x3*y1*y2^2*y3-8*x1*x3*y1*y2^2*y3-4*x2^2*y1*y2^2*y3+4*x1*x2*y1*y2^2*y3+2*x1^2*y1*y2^2*y3
-2*y1^4*y2*y3+2*x3^2*y1^2*y2*y3-8*x2*x3*y1^2*y2*y3+4*x1*x3*y1^2*y2*y3+2*x2^2*y1^2*y2*y3+4*x1*x2*y1^2*y2*y3-4*x1^2*y1^2*y2*y3-2*x2^2*x3^2*y2*y3+4*x1*
x2*x3^2*y2*y3-2*x1^2*x3^2*y2*y3+4*x1*x2^2*x3*y2*y3-8*x1^2*x2*x3*y2*y3+4*x1^3*x3*y2*y3-2*x1^2*x2^2*y2*y3+4*x1^3*x2*y2*y3-2*x1^4*y2*y3-2*x3^2*y1^3*y3+4
*x2*x3*y1^3*y3-2*x2^2*y1^3*y3-2*x2^2*x3^2*y1*y3+4*x1*x2*x3^2*y1*y3-2*x1^2*x3^2*y1*y3+4*x2^3*x3*y1*y3-8*x1*x2^2*x3*y1*y3+4*x1^2*x2*x3*y1*y3-2*x2^4*y1*
y3+4*x1*x2^3*y1*y3-2*x1^2*x2^2*y1*y3+y1^2*y2^4+x3^2*y2^4-2*x1*x3*y2^4+x1^2*y2^4-2*y1^3*y2^3-2*x3^2*y1*y2^3+4*x1*x3*y1*y2^3-2*x1^2*y1*y2^3+y1^4*y2^2+2*
x3^2*y1^2*y2^2-2*x2*x3*y1^2*y2^2-2*x1*x3*y1^2*y2^2+2*x2^2*y1^2*y2^2-2*x1*x2*y1^2*y2^2+2*x1^2*y1^2*y2^2+x3^4*y2^2-2*x2*x3^3*y2^2-2*x1*x3^3*y2^2+2*x2^2*x3^2*y2^2
+2*x1*x2*x3^2*y2^2+2*x1^2*x3^2*y2^2-4*x1*x2^2*x3*y2^2+2*x1^2*x2*x3*y2^2-2*x1^3*x3*y2^2+2*x1^2*x2^2*y2^2-2*x1^3*x2*y2^2+x1^4*y2^2-2*x3^2*y1^3*y2+4*x2*x3*y1^3*
y2-2*x2^2*y1^3*y2-2*x3^4*y1*y2+4*x2*x3^3*y1*y2+4*x1*x3^3*y1*y2-2*x2^2*x3^2*y1*y2-8*x1*x2*x3^2*y1*y2-2*x1^2*x3^2*y1*y2+4*x1*x2^2*x3*y1*y2+4*x1^2*x2*x3
*y1*y2-2*x1^2*x2^2*y1*y2+x3^2*y1^4-2*x2*x3*y1^4+x2^2*y1^4+x3^4*y1^2-2*x2*x3^3*y1^2-2*x1*x3^3*y1^2+2*x2^2*x3^2*y1^2+2*x1*x2*x3^2*y1^2+2*x1^2*x3^2*y1^2-2*x2^3*
x3*y1^2+2*x1*x2^2*x3*y1^2-4*x1^2*x2*x3*y1^2+x2^4*y1^2-2*x1*x2^3*y1^2+2*x1^2*x2^2*y1^2+x2^2*x3^4-2*x1*x2*x3^4+x1^2*x3^4-2*x2^3*x3^3+2*x1*x2^2*x3^3+2*x1^2*x2*
x3^3-2*x1^3*x3^3+x2^4*x3^2+2*x1*x2^3*x3^2-6*x1^2*x2^2*x3^2+2*x1^3*x2*x3^2+x1^4*x3^2-2*x1*x2^4*x3+2*x1^2*x2^3*x3+2*x1^3*x2^2*x3-2*x1^4*x2*x3+x1^2*x2^4-2*x1^3
*x2^3+x1^4*x2^2))/((2*x2-2*x1)*y3+(2*x1-2*x3)*y2+(2*x3-2*x2)*y1);
1
0
0
1
-1
0
1.0 <---- aprēķinātais rādiuss ir pareizs.
Mēģinājumi vienkāršot atrisinājumu, savelkot līdzīgos locekļus vai iznesot pirms iekavām kopējos reizinātājus, nedod būtiskus rezultātus. Apjomīgā izteiksme varētu būt pārsteigums – kāpēc tik vienkāršam uzdevumam ir tik sarežģīts atrisinājums. Domāju, ka izskaidrojums varētu būt tajā, ka katrs no 6 skaitļiem (koordinātēm) ietekmē rezultātu (rādiusu) sarežģītā mijiedarbībā ar katru no pārējiem 5 skaitļiem, tādēļ arī izteiksmē tik daudz locekļu, kur katra koordināte reizināta pati ar sevi un citām koordinātēm dažādās pakāpēs.
Mg.phys. Andris Mednis