This function has a universal attracting fixed point at the Dottie number.
This function has a universal attracting fixed point at the Dottie number. Its hyperbolic analogue describes the shape of a catenary. The limit as x approaches 0, of this function minus 1, all over x, equals 0, an intermediate step in proving that its first derivative is its negative cofunction. Its namesake law is a generalization of the Pythagorean Theorem. Positive in the first and fourth quadrants, in a right triangle it is the adjacent leg over the hypotenuse. For 10 points, name this even trigonometric function which is the reciprocal of secant and the cofunction of sine.
This function has a universal attracting fixed point at the Dottie number.
{cosine} function [accept things like {cos x} or {cos} ?]