Trigonometric Functions
Function (abbreviation)	Definition	Formula
sine (sin)	$opposite/hypotenuse$	sin A = $a/c$
cosine (cos)	$adjacent/hypotenuse$	cos A = $b/c$
tangent (tan)	$opposite/adjacent$	tan A = $a/b$
cotangent (cot or ctn)	$adjacent/opposite$	cot A = $b/a$
secant (sec)	$hypotenuse/adjacent$	sec A = $c/b$
cosecant (csc)	$hypotenuse/opposite$	csc A = $c/a$

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2007, Columbia University Press. All rights reserved.

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