co·tan·gent 
(kō-tănjənt, kōtăn′-)
(kō-tănjənt, kōtăn′-)n. Abbr. cot
1. The reciprocal of the tangent of an angle in a right triangle.
2. The tangent of the complement of a directed angle or arc.
co′tan·gential (-jĕnshəl) adj.
cotangentcot θ = b/a