Definition:Tangent


 * Geometry
 * A curve is tangent to another curve if it touches that curve but does not cross it.


 * Analytic Geometry
 * A straight line is tangent to a curve if it intersects that curve locally at exactly one point.


 * Trigonometry
 * The tangent of an angle $\theta$ is a function defined as the opposite side divided by the adjacent.


 * Analysis
 * The tangent of a real number $x$ is defined as the extension of the tangent of an angle to the real numbers.


 * Complex Analysis
 * The tangent of a complex number $z$ is defined as the extension of the tangent of a real number to the complex plane.