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Cake day: April 9th, 2021

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  • Lvxferre@lemmy.mlto4chan@lemmy.worldA math lesson from 4chan
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    10 months ago

    That’s surprisingly accurate, as people here are highlighting (it makes geometrical sense when dealing with complex numbers).

    My nephew once asked me this question. The way that I explained it was like this:

    • the friend of my friend is my friend; (+1)*(+1) = (+1)
    • the enemy of my friend is my enemy; (+1)*(-1) = (-1)
    • the friend of my enemy is my enemy; (-1)*(+1) = (-1)
    • the enemy of my enemy is my friend; (-1)*(-1) = (+1)

    It’s a different analogy but it makes intuitive sense, even for kids. And it works nice as mnemonic too.








  • Glacial = anhydrous. People call it this way because pure acetic acid has a rather high freezing point (16°C), and it looks a lot like plain ice when frozen. (It still stinks vinegar once you open the bottle though.) But once you add even a bit of water, the freezing point drops considerably, so acetic acid solutions don’t show the same “ice”.

    So in colder days, you need to rewarm it back into a liquid. Then people get really sloppy (I know it not just from that professor’s anecdote, but from watching it). They say “I’m just rewarming it, and it’s just acetic acid, what could go wrong?”. Well, it’s still a big flask of a corrosive, volatile, and flammable substance.

    In the meantime, the same people doing dangerous reactions like nitration (it literally explodes if you let it get too hot - spreading nitric acid, sulphuric acid, and some carcinogenic solvent) “miraculously” pay full attention, obsessively taking care of the temperature of the ice bath.

    Part of the advice that I mentioned in that comment chain is that - smaller dangers are still dangers, do not underestimate them.



  • Most “rules of thumb” become awful advice when used indiscriminately.

    People assign slightly different meanings to the same words. You need to acknowledge this to understand what they say.

    Words also change meaning depending on the context.

    When you still don’t get what someone else said, it’s often more useful to think that you’re lacking a key piece of info than to assume that the other person does.

    Hell is paved with good intentions. This piece of advice is popular, but still not heard enough.

    Related to the above: if someone in your life is consistently rushing towards conclusions, based on little to no information, minimise the impact of that person in your life.

    Have at least one recipe using leftovers of other recipes. It’ll reduce waste.

    Alcohol vinegar is bland, boring, and awful for cooking. But it’s a great cleaning agent.

    Identify what you need to keep vs. throw away. Don’t “default” this indiscriminately, analyse it on a per case basis.

    The world does not revolve around your belly button and nature won’t “magically” change because of your feelings.

    You can cultivate herbs in a backyard. No backyard? Flower pots. No flower pots? Old margarine pot. (Check which herbs grow well where you live.)










  • Isn’t lol short for “laughing out loud”?

    Wiktionary lists both “laughing out loud” and “lots of laughs”. Nowadays though it’s neither; on a pragmatic level it doesn’t convey “I’m laughing” / “I laughed”, it conveys amusement and/or lack of seriousness, depending on the context.

    • [Alice] The Sun is a star.
    • [Bob] yeah sure the sun only appears at night lol (implying: “I’m amused at what Alice said, and I don’t take it seriously.”)