Merriam-Webster's Collegiate Dictionary
tan·gent \\ˈtan-jənt\\ adjective ETYMOLOGY Latin tangent-, tangens, present participle of tangere to touch; perhaps akin to Old English thaccian to touch gently, stroke
DATE 1594
1.
a. meeting a curve or surface in a single point if a sufficiently small interval is considered
straight line tangent to a curve
b.
(1) having a common tangent line at a point
tangent curves
(2) having a common tangent plane at a point
tangent surfaces2. diverging from an original purpose or course : irrelevant
tangent remarksnoun ETYMOLOGY New Latin tangent-, tangens, from linea tangens tangent line
DATE 1594
1.
a. the trigonometric function that for an acute angle is the ratio between the leg opposite to the angle when it is considered part of a right triangle and the leg adjacent
b. a trigonometric function that is equal to the sine divided by the cosine for all real numbers θ for which the cosine is not equal to zero and is exactly equal to the tangent of an angle of measure θ in radians2. a line that is tangent; specifically : a straight line that is the limiting position of a secant of a curve through a fixed point and a variable point on the curve as the variable point approaches the fixed point3. an abrupt change of course : digression
the speaker went off on a tangent4. a small upright flat-ended metal pin at the inner end of a clavichord key that strikes the string to produce the tone tangent
tangent (adj.)
1590s, "meeting at a point without intersecting," from L. tangentem (nom. tangens), prp. of tangere "to touch," from PIE base *tag- "to touch, to handle" (cf. L. tactus "touch," Gk. tetagon "having seized," O.E. þaccian "stroke, strike gently"). First used by Dan. mathematician Thomas Fincke in "Geomietria Rotundi" (1583). The noun also is attested from 1590s; extended sense of "slightly connected with a subject" is first recorded 1825.
Oxford Advanced Learner's Dictionary-牛津双解-OALD7
tangenttan·gent /
5tAndVEnt /
noun1. (geometry 几何) a straight line that touches the outside of a curve but does not cross it
切线2. (
abbr. tan)
(mathematics 数) the
ratio
of the length of the side opposite an angle in a
right-angled
triangle to the length of the side next to it
正切⇨ compare
cosine
,
sine
IDIOMS ▪ fly / go off at a 'tangent(BrE) (
NAmE go off on a 'tangent) (
informal)
to suddenly start saying or doing sth that does not seem to be connected to what has gone before
突然转换话题;突然改变行动 Webster's Third New International Dictionary, Unabridged
tan·gentI. \ˈtanjənt, ˈtaan-\
adjectiveEtymology: Latin
tangent-, tangens, present participle of
tangere to touch; akin to Greek
tetagōn having seized, Old English
thaccian to stroke, touch gently
1.
a. : touching at a single point
< a straight line tangent to a curve >
b.
(1) : having a common tangent line at a point — used of two curves in a plane, two space curves, or a surface and a space curve
(2) : having a common tangent plane at a point — used of two surfaces
2.
a. : diverging from an original purpose or course
: erratic
< much of his work is chaotic and distorted by tangent obsessions — Tennessee Williams >
b. : contiguous
: being in agreement
< subject matter tangent to the country's growth in those years — M.F.Milton >II. noun
(
-s)
Etymology: New Latin
tangent-, tangens, from Latin, present participle of
tangere to touch
1.
a. : tangent line
b. : the ordinate of any point on the terminal side of an angle divided by the nonzero abscissa of this point with the vertex coinciding with the origin of a plane rectangular coordinate system and the initial side of the angle coinciding with the positive x-axis — abbr.
tan2. : a course abruptly deviating from that previously pursued
: digression
,
irrelevancy
< avoid wandering off on tangents — J.F.Wharton >
< his critics … went off at a tangent — Saul Carson >3. : a small upright flat-ended metal pin at the inner end of a clavichord key that strikes the string to produce the musical tone and fixes the pitch by damping the string
4. : a piece of straight railroad track
III. noun: a trigonometric function that is equal to the sine divided by the cosine for all real numbers θ for which the cosine is not equal to zero and is exactly equal to the tangent of an angle of measure θ in radians
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inverse tangent
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