Its Maclaurin series is one minus x squared over two factorial, plus x to the fourth over four factorial, et cetera; and its namesake law generalizes the Pythagorean theorem.
One law concerning this function describes the radiant intensity from a certain type of surface, and is named for Lambert. The hyperbolic version of this function defines a catenary, and equals half the quantity e to the x plus e to the negative x. A double-angle identity for this function is that with an input of two theta, it equals the quantity one minus the tangent squared of theta over the quantity one plus the tangent squared of theta. Its Maclaurin series is one minus x squared over two factorial, plus x to the fourth over four factorial, et cetera; and its namesake law generalizes the Pythagorean theorem. Name this trigonometric function that, for an angle in a right triangle, equals the ratio of the adjacent side to the hypotenuse.
One law concerning this function describes the radiant intensity from a certain type of surface, and is named for Lambert.
{cosine} function [or {f} of x equals {cosine} of x, etc.]