A straight line is tangent to a given curve at a point on the curve if the line passes through the point on the curve and has slope , where is the Derivative of .
See also Circle Tangents, Secant Line, Tangent, Tangent Plane, Tangent Space, Tangent Vector
Yates, R. C. ``Instantaneous Center of Rotation and the Construction of Some Tangents.''
A Handbook on Curves and Their Properties. Ann Arbor, MI: J. W. Edwards, pp. 119-122, 1952.