this post was submitted on 11 Jan 2024
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A math lesson from 4chan (sh.itjust.works)
submitted 1 year ago by [email protected] to c/[email protected]
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[–] [email protected] 10 points 1 year ago* (last edited 1 year ago) (2 children)

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.

[–] [email protected] 1 points 1 year ago

It’s a different analogy but it makes intuitive sense, even for kids.

Its good maths but terrible realpolitick.

[–] [email protected] 1 points 1 year ago

I teach maths and one of the analogies is use is watching a film of someone walking forwards and backwards. If you play the film forwards (multiplying by positive), you can see the person walking forwards and backwards as normal. If you play the film backwards (multiplying by negative) you see the opposite. So multiplying by negative reverses whatever was happening before. Hard to put into words but the visuals (hopefully) seem to explain it well enough.