Watch this 20 minute 3blue1brown video giving a beautiful proof of the Basel problem using lighthouses. Watch actively: pause, rewind, take notes if that helps. Figure it out.
Today in class we discussed the intuition behind Corollary 2.22, 2.24 and a problem related to 2.25 in your text. Please read pages 60-62 carefully and solidify your understanding.
We proved Theorem 2.27 in class (modulo some details), but the textbook doesn’t. Although he does make a margin note (19) which could be turned into a different proof than the one I gave. For the source of the proof I gave in class, see ‘Lectures.’
Homework due next Friday has been posted.
On the Lectures page, I posted some links and further info to do with the Rabbit & Hare problem, and the Postage Stamp problem, which you may have enjoyed exploring on your recent homework.