Koosinusfunktsiooni

Koosinusfunktsiooni, commonly known as the cosine function in English, is a fundamental trigonometric function. It relates an angle of a right-angled triangle to the ratio of the length of the adjacent side to the length of the hypotenuse. Mathematically, for an angle theta in a right-angled triangle, cosine(theta) = adjacent / hypotenuse.

The cosine function is periodic with a period of 2π radians or 360 degrees. Its graph is a smooth, wave-like curve. The values of the cosine function range from -1 to 1, inclusive. It is an even function, meaning that cos(-x) = cos(x) for all x. Key values include cos(0) = 1, cos(π/2) = 0, cos(π) = -1, and cos(3π/2) = 0.

The cosine function has numerous applications in various fields, including physics, engineering, signal processing, and mathematics itself. It is used in the study of oscillations, waves, and periodic phenomena. It is also a crucial component in Fourier analysis and complex number representations. The cosine function is closely related to the sine function, with the identity cos(x) = sin(π/2 - x).