tangent
noun [ C ] mathematics specialized uk/ˈtæn.dʒənt/ us/ˈtæn.dʒənt/
(CIRCLE)
切线
a straight line that touches but does not cut into a curve
(TRIANGLE)
(written abbreviation tan)正切
(in a triangle that has one angle of 90°) the ratio of the length of the side opposite an angle less than 90° divided by the length of the shorter of the two sides that are next to the angle
Compare: cosine sine
Idiom
go off on a tangentidiom (UK also go/fly off at a tangent) 突然离题;突然离开原来的思路
to suddenly start talking or thinking about a completely new subject
It's hard to get a firm decision out of him - he's always going off on a tangent. 很难从他那里得到一个明确的答复——他老是突然离题扯别的去了。