One of many is knowing the exact value of pi which is a circle's circumference divided by its diameter.
That's hard to say.
The question is not clear. Hardest, as in the most rigid, is a triangular prism (or tetrahedron). Hardest, to work the geometry of, is probably an irregular blob.
the hardest pitch ever was 106 mph
The hardest challenge I've ever faced is life.
The hardest math problem ever Also, according to True Jackson V.P, the answer is 16. I paused the screen showing the problem, and x=16
Foucault's last conundrum.Fermi's last theromExact value of Pi.
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brainteasers
Geometry is a VERY broad subject, you need to be more specific.
I am pretty sure you can make them as hard as you want - if you have a "hard" problem, you can always find one that is even harder. If this is true, then there is no such thing as a "hardest algebra problem".
Diamond. a very hard material that is the hardest substance ever, or at least discover to be the hardest substance on EARTH THAT IS
Fedor Emelianenko