Editing Horizontal line test (section)

{{Short description|Test for the injectivity of a function}}
In [[mathematics]], the '''horizontal line test''' is a test used to determine whether a [[function (mathematics)|function]] is [[injective]] (i.e., one-to-one).<ref name="Stewart">{{cite book|last=Stewart|first=James|title=Single Variable Calculus: Early Transcendentals|year=2003|publisher=Brook/Cole|location=Toronto ON|isbn=0-534-39330-6|pages=[https://archive.org/details/singlevariableca00stew/page/64 64]|url=https://archive.org/details/singlevariableca00stew/page/64|edition=5th.|authorlink=James Stewart (mathematician)|accessdate=15 July 2012|quote=Therefore, we have the following geometric method for determining whether a function is one-to-one.|url-access=registration}}</ref>