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Tan·gent n. Geom. A tangent line curve, or surface; specifically, that portion of the straight line tangent to a curve that is between the point of tangency and a given line, the given line being, for example, the axis of abscissas, or a radius of a circle produced. See Trigonometrical function, under Function.

**Artificial tangent**, *or* **Logarithmic tangent**, the logarithm of the natural tangent of an arc.

**Natural tangent**, a decimal expressing the length of the tangent of an arc, the radius being reckoned unity.

**Tangent galvanometer** Elec., a form of galvanometer having a circular coil and a short needle, in which the tangent of the angle of deflection of the needle is proportional to the strength of the current.

**Tangent of an angle**, the natural tangent of the arc subtending or measuring the angle.

**Tangent of an arc**, a right line, as *ta*, touching the arc of a circle at one extremity *a*, and terminated by a line *ct*, passing from the center through the other extremity *o*.