This file is from Wikimedia Commons and may be used by other projects.
The description on its file description page there is shown below.
Summary
DescriptionInduction step 1728668638527.jpg
English: Induction step in the euclidean geometric proof of the Basel problem. The sum of inverse squares of distances of P1 and P2 from Q equals the inverse square distance from P to Q.
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.
http://creativecommons.org/publicdomain/zero/1.0/deed.enCC0Creative Commons Zero, Public Domain Dedicationfalsefalse
Captions
Induction step in the euclidean geometric proof of the Basel problem. The sum of inverse squares of distances of P1 and P2 from Q equals the inverse square distance from P to Q.