PythagoreanIdentity

Trigonometric knows sin(a)^2 + cos(a)^2 as a node of two
operands, and the simplifier sorts a sum so that the pair lands adjacent -- which
puts them in one node only when nothing sorts before them: sqrt(2) + sin(t)^2
+ cos(t)^2 is (sqrt(2) + cos(t)^2) + sin(t)^2, and stayed so, while
a + sin(t)^2 + cos(t)^2, whose a sorts last, became 1 + a. This
set is the n-ary reading of the same identity,
PythagoreanIdentity, which finds the two squares
among any number of operands. Run beside Trigonometric by the simplifier
rather than listed in All: it is one identity the trigonometric set
already claims, in the shape the matcher can see.
https://github.com/asc-community/AngouriMath/issues/725