Your geometry puzzle for the day involves a Stieglitz photo of a sculpture that may be by Duchamp (or maybe by a female friend of Duchamp from whom Duchamp stole the glory, that's not the point):
en.wikipedia.org/wiki/File:Mar

It was created by rotating a commercial urinal from its usual position.
Assuming that the photo is from where you would stand in front of either object, by what angle was it rotated, around what axis?

Why? Because we've been arguing about it on Wikipedia, of course, why else?

@11011110 Reflected across the plane y+z=0, where (to a normal standing viewer) +x is to the right, +y is directly forward, and +z is up. Or, if you must, rotated 1/2 turn around the line x=y+z=0.

@jeffgerickson It would be interesting to have watched Duchamp carry out the reflection.

@11011110 But isn't the canonical answer “A fish”?

A Mastodon instance for maths people. The kind of people who make $\pi z^2 \times a$ jokes.

Use $ and $ for inline LaTeX, and $ and $ for display mode.