《集合·几何：一份化圆为方指南》
https://tracewind.net/science/1261.html
BY 风痕的图书架
Telegram is riding high, adding tens of million of users this year. Now the bill is coming due.Telegram is one of the few significant social-media challengers to Facebook Inc., FB -1.90% on a trajectory toward one billion users active each month by the end of 2022, up from roughly 550 million today.
Telegram is a free app and runs on donations. According to a blog on the telegram: We believe in fast and secure messaging that is also 100% free. Pavel Durov, who shares our vision, supplied Telegram with a generous donation, so we have quite enough money for the time being. If Telegram runs out, we will introduce non-essential paid options to support the infrastructure and finance developer salaries. But making profits will never be an end-goal for Telegram.
风痕的图书架 from hk