Tangential angle

The tangential angle φ for an arbitrary curve A in P.

In geometry, the tangential angle of a curve in the Cartesian plane, at a specific point, is the angle between the tangent line to the curve at the given point and the x-axis.[1] (Some authors define the angle as the deviation from the direction of the curve at some fixed starting point. This is equivalent to the definition given here by the addition of a constant to the angle or by rotating the curve.[2])

  1. ^ Weisstein, Eric W. "Natural Equation". MathWorld.
  2. ^ For example: Whewell, W. (1849). "Of the Intrinsic Equation of a Curve, and Its Application". Cambridge Philosophical Transactions. 8: 659–671. This paper uses φ to mean the angle between the tangent and tangent at the origin. This is the paper introducing the Whewell equation, an application of the tangential angle.