Hi, I was wondering if polyphasic sleep is dangerous? What kinds of long term health effects could it have? Did anyone try it?

Hi, i need to study Mathematics from scratch. I didn't learn any math at school. I'm from a EU country, not UK.

I have a hard time finding math books that use the metric system online. I try'd openstax, but those books use imperial dogshit. https://openstax.org/ I try to scavenge anna's archive. But all of them imperial. And all UK Secondary School books online are incomplete. I can't just buy/import them because i have not been in school for over a decade. Only teachers can buy them.

I need pure metric Math e-books for prealgebra, algebra 1&2, Trigonometry, Geometry, Precalculus, Calculus. I want to put them om my e-reader with wacom stylus, so i don't need to buy paper.

If i have to use imperial measurements for longer than an hour, my brain will explode. 🤯 I'm not looking forward to converting and typesetting hundreds of books in LaTeX on Arch linux.

Which books should i get? Only complete books.