Since the changes in Twitter (now X), I have not been able to see the posts, not being a subscriber. But I noticed poking around that some twitter accounts were still viewable. However, like some demented aging octogenarian they had lost track of time, that is, instead of being sorted with the most recent post first, they showed a random scattering of posts from different times. So a current post could be right next to one several years ago. That is what I discovered with the now defunct MathsMonday site. I found a post from 10 May 2021 that I had not seen before, namely,

“The points A and B are on the curve y = x^{2} such that AOB is a right angle. What points A and B will give the smallest possible area for the triangle AOB?”

Answer.

See the Pythagorean Parabola Puzzle for solution.

**(Update 9/1/2023) Elegant Alternative Solution by Oscar Rojas**

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