co·tan·gent /(ˌ)koˈtænʤənt, ˈkoˌ/
  餘切
  Co·tan·gent n.  Trig. The tangent of the complement of an arc or angle. See Illust. of Functions.
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  cotangent
       n : ratio of the adjacent to the opposite side of a right-angled
           triangle [syn: cotan]