cos4

Cos4 is a shorthand for the evaluation of the cosine function at the numerical argument 4, commonly written as cos(4). In mathematics, arguments to trigonometric functions are typically given in radians unless a different unit is specified. Therefore cos4 denotes the cosine of 4 radians.

Its value is a real number between -1 and 1. Numerically, cos(4) ≈ -0.6536436208627366. This corresponds to an angle of about 229.183 degrees when converted from radians.

Because the cosine function is periodic with period 2π, cos(4) equals cos(4 ± 2πk) for any integer k. It can be related to other trigonometric values via identities, for example cos(4) = 2cos^2(2) − 1. If exact closed forms are required, they rely on cos(2) or cos(1) expressed with numerical approximations.

Applications of cos(4) occur in numerical computations, Fourier analysis, and signal processing as part of evaluating trigonometric terms at specific angles.

See also: cosine, trigonometric functions, radians, Chebyshev polynomials, unit circle.