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The photographs below show an interesting triangle that may bother some people.


If this bothers you, you are invited to explain how this setup works.
I believe:
(a) the pendulum is swinging through the triangle; so what!
(b) the pendulum is swinging behind the triangle.
(c) this is another trick using a computer animation.
(d) the "triangle" is formed using three orthogonal square rods.