HalfTurn​(AngouriMath.​Entity.​Number.​Complex)

Every angle in the tables below is written 2pi/n, so they name nothing at
all between 2pi/5 and 2pi/3 -- the whole lower half of the circle
is missing, and most of the second quadrant with it. The identities each Pull
tries reach some of what is missing and not the rest, which is why
sin(2pi/3) was answered exactly while its neighbour sin(5pi/3), the
same value negated, was left as written. Turning the argument by half a circle
and taking the sign back is what the tables are short of. It is applied once,
around the lookups rather than inside them, so it cannot turn back and loop.
https://github.com/asc-community/AngouriMath/issues/743