cosd

Cosd is a trigonometric function that computes the cosine of an angle expressed in degrees. It is defined as cosd(x) = cos(x × π/180), where the inner cosine operates on radians. In other words, cosd converts the input from degrees to radians before applying the standard cosine function.

The function accepts inputs of various shapes, including scalars, vectors, matrices, and higher-dimensional arrays, and evaluates the result element-wise. The output shares the same dimensions as the input and is guaranteed to lie in the interval [-1, 1], consistent with the cosine function.

Cosd inherits the standard properties of cosine: it is even, meaning cosd(-x) = cosd(x), and it has a period of 360 degrees, so cosd(x + 360n) = cosd(x) for any integer n. Inverse operations are provided separately in the form of acosd, which returns an angle in degrees when given a cosine value.

Cosd is commonly available in mathematical computing environments such as MATLAB and GNU Octave. In environments that only provide radians-based cosine, cosd is emulated by taking the radian conversion explicitly, for example by using cos(deg2rad(x)).

Typical usage examples include cosd(60) = 0.5 and cosd(180) = -1. Applications span engineering, physics, navigation, and any domain where angles are naturally expressed in degrees rather than radians. Related functions include sind and tand for sine and tangent in degrees, as well as their inverse counterparts acosd, asind, and atand.