Categories
Mathématiques (French)

Pourquoi la somme des angles d’un triangle fait-elle 180° ?

Introduction

Un triangle quelconque ABCJe me suis toujours demandé pourquoi la somme des angles d’un triangle était constante et égale à 180°. Comment parvient-on à une telle affirmation ?

L’histoire raconte que Blaise Pascal (mathématicien français du XVII ième siècle) aurait démontré cette proposition d’Euclide à l’âge de 11 ans … cela m’a toujours fasciné.

Comment un enfant de seulement 11 ans a-t-il bien pu parvenir à ce résultat ?!?

Bizarrement, une réponse m’est venue un jour sous la douche, alors que j’y pensais sans vraiment y réfléchir 🙂

Le raisonnement est géométrique et plutôt intuitif. Les figures se sont formées dans mon esprit et la solution m’est apparue d’un coup comme une évidence.

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Categories
Plongée (French)

Pourquoi prend-on 1 bar tous les 10m ?

Under Water
Rays of sun under water. The ocean is quiet.

Les plongeurs le savent bien : tous les 10 mètres, la pression à laquelle nous sommes soumis augmente d’1 bar.

Mais en fait pourquoi ?

Dans cet article, nous allons faire un peu de science physique. Rien de trop compliqué rassurez-vous.

En réalité, il s’agit de comprendre ce qu’est la pression, de différencier la masse et le poids, puis de jouer avec quelques conversions d’unités.

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Categories
System Admin

Joplin At Rest Encryption With Tomb On Linux

Spooky Graveyard

To Encrypt At Rest Or Not To?

There has been a lot of (passionate) debates on Joplin’s forum about its SQLite 3 database showing everything in clear text.

And by everything, I literally mean “everything”. Including your master encryption password.

Now, my intention here isn’t to fuel another debate. Joplin passed several security audits. Long story short: if you want your computer to remain safe (as much as possible), encrypt your whole hard-drive.

This is indeed a best practice.

Instead of discussing whether or not Joplin should encrypt its database, I’ll share the additional layer of security I laid out on my Linux machines using tomb.

By the way, if you have no idea what I’m talking about (what the hell is Joplin?), I suggest you read my previous post: From Evernote To Joplin.

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Categories
Miscellaneous

From Evernote To Joplin

Joplin's Application Icon
Joplin’s Application Icon

I recently came across Joplin.

Simply put, Joplin is a free open source replacement for Evernote.

I’m an Evernote subscriber. However, I don’t use it that much. And I don’t have that many notes.

Let me be clear: Evernote offers a brilliant service, there is no denying that, it’s absolutely great and super convenient. But, in my case, for less than a 100 notes, I’m not fully convinced it’s worth the price.

Furthermore, Joplin has a few “punchy” arguments to put in a fair fight:

  • It’s free and open source (I know, I already said that, but it’s important).
  • It’s cross-platform (nodejs to the core). There are apps for Windows, MacOS, Linux, Android, and iOS. There is even an app to use it on the command line (Vim style)!
  • It works locally (no need for an internet connection), but enables synchronization with remote sharing services. Thus Yes! It can sync your notes across devices (using the WebDAV protocol).
  • It supports end-to-end encryption with zero knowledge: notes are encrypted locally before being transferred.
  • It integrates fully with Nextcloud!

Honestly, if the first few arguments weren’t enough, although I was definitely intrigued, the last 2 won me on the spot.

So let’s have a look at the beast.

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Categories
System Admin

Raspberry Pi: Hands On

Raspberry Pi a computer the size of a credit card
Raspberry Pi a computer the size of a credit card

Today I’ll share the very first configuration steps I usually take when I get my hands on a brand new raspberry pi.

I assume that:

  • Raspbian is freshly installed.
  • The raspberry pi is up and running.
  • You know its IP address.
  • You know how to connect to the pi over ssh.
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Categories
Miscellaneous

A Phoenix Rising From The Ashes

Egyption phoenix the burning bird
Egyption phoenix the burning bird

Hello world !

Yes, I know, it’s a weird title for a post. The rationale is simple though. I’ve had many blogs over the years. This is my latest attempt.

I guess it all started with Gladys … Nope, it’s not what you think.

Gladys is a French open source project. It’s a raspberry pi based house automation platform. It gave the nerd in me the nudge I needed. I started refreshing my javascript and debian knowledge, write tutorials, both for the community and to track everything I was building up.

Then it hit me ! Why keep this to myself on Evernote when I could share with everyone to whom it might be helpful ?

One topic led to another and there I am, starting a blog … again.

Expect tutorials on a variety of topics, among which: debian linux, raspberry pies, Gladys, photography, guitar playing … well, whatever crosses my mind, that I believe could be interesting to not just me.

Happy reading.