Trigonometric

Forty-three arms become thirty-three. Ten of the arms are five rules written
twice, once for each order of a commutative pair — a sine times a cosine, an arcsine
plus an arccosine, a tangent times a cotangent, and so on — and a commutative pattern
says each once. The rest are genuinely distinct identities, several of them carrying
the interval conditions that
#884 and
#887 are about,
and those conditions are now attached to the rule they belong to rather than to the
set.