sb. (a.) Trig. [f. CO- pref. 4 + TANGENT. The L. cotangens is used by Gunther, Canon Triangulorum, 1620.] The tangent of the complement of a given angle. (Abbrev. cot.)

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1635.  J. W[ells], Sciographia, 47. So is the tangent of R Z P To the cotangent of R P Z.

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1704.  Harris (cited by Johnson).

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1706.  Phillips (ed. Kersey), Co-tangent is the Tangent of an Arch of a Circle, which is the Complement of another to 90 Degrees.

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1831.  Brewster, Optics, xix. 170. The index of refraction is the cotangent of the angle of polarisation.

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1852.  De Morgan, in R. P. Graves, Life Sir W. R. Hamilton, III. 387. Put cosines in the middle, sines on the flanks, and cotans on the extreme flanks.

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  B.  adj. Cotangent line = cotangent.

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1652.  Stirrup, Horometria, IV. i. (1659), 107. The side D E … (for distinction) may be called a Tangent line, and the side F F a Co-tangent line.

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