恆等式

identity (math.)

surname Heng

permanent / constant / fixed / usual / ordinary / rule (old) / one of the 64 hexagrams of the Book of Changes (䷟)

identity ≡ (math., logic) / identical

class / rank / grade / equal to / same as / to wait for / to await / et cetera / and so on / et al. (and other authors) / after / as soon as / once

an equality / an equation

type / form / pattern / style