[ koh-tan-juh nt, koh-tan- ]
/ koʊˈtæn dʒənt, ˈkoʊˌtæn- /

noun Trigonometry.

(in a right triangle) the ratio of the side adjacent to a given angle to the side opposite.
the tangent of the complement, or the reciprocal of the tangent, of a given angle or arc. Abbreviation: cot, ctn
Also co·tan [koh-tan] /ˈkoʊˌtæn/.

Origin of cotangent

First recorded in 1625–35, cotangent is from the New Latin word cotangent- (stem of cotangēns). See co-, tangent

Related forms

co·tan·gen·tial [koh-tan-jen-shuh l] /ˌkoʊ tænˈdʒɛn ʃəl/, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for cotan (1 of 2)


/ (ˈkəʊˌtæn) /

abbreviation for


British Dictionary definitions for cotan (2 of 2)


/ (kəʊˈtændʒənt) /


(of an angle) a trigonometric function that in a right-angled triangle is the ratio of the length of the adjacent side to that of the opposite side; the reciprocal of tangentAbbreviation: cot, cotan, ctn

Derived Forms

cotangential (ˌkəʊtænˈdʒɛnʃəl), adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Science definitions for cotan


[ kō-tănjənt ]

The ratio of the length of the adjacent side of an acute angle in a right triangle to the length of the opposite side. The cotangent is the inverse of the tangent.
The ratio of the ordinate to the abscissa of the endpoint of an arc of a unit circle centered at the origin of a Cartesian coordinate system, the arc being of length x and measured counterclockwise from the point (1, 0) if x is positive or clockwise if x is negative.
A function of a number x, equal to the cotangent of an angle whose measure in radians is equal to x.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.