Squaring the Circle
The classic construction with only compass and lineal is impossible.
But if you allow one extra angle of arccos(sqrt(π)/2)≈27,597°, then you can square any circle! The driven length is sqrt(π) and the square has an area of π.

Mushrooms seen on my way home.
There was a large three beside them in the past, which was removed.
I think remains of the large roots are still in the ground and are broken down by the mycelia.
#fungus #nature #mushroom