Daily mathematics serial 55: February 24

2 month 24 Japan XXIV

Mathematical maxims

A real scientist , Especially mathematicians , Like an artist , Experience the same impression at work ; Enjoy the same nature 、 The same great pleasure .—— Henry · Poincare （Henri Poincaré）

Math exercises

It's Monday , Tom and Jerry do the same job . When Tom should go home , Jerry wouldn't let him go , Why? ？

Ancient and Modern Commentaries

Encryption technology （Encryption technology） It is one of the hottest research fields now . It guarantees the secrecy of telex messages —— Whether they are government secrets 、 Financial information 、 Medical information 、 Company secrets , Or other secrets . At present, we are studying to apply an old method to the new packaging technology . Recall how we hid our secrets in a message , Only those perforated cassettes can find out what the expected secret is . At present, electronic information is being used to study that design method . The sender makes the expected secret into encrypted small electronic data packets and mixes them with other electronic data packets , The receiver knows how to get rid of useless packets and retain important information . This method is called “ Sieve bran method ”（chaffing & winnowing）.

For the first time to use ≤ And ≥

Pierre · Bugai （Pierre Bouguer） stay 1734 First used in ≥ \ge