What is the definition of cosine function?

Answer by  esteban (1334)

In a right triangle, the cosine of either of the acute angles is the ratio between the length of the side adjacent to the angle and the length of the hypotenuse. The cosine of a right angle is 0.

Answer by  anrimala36 (208)

Picture a circle (radius=1) centered at (0,0). Draw a radius, then connect it to another line segment perpendicular to the x-axis; connect that to the origin to form a triangle. The cosine is (the length of the adjacent side [x-value)])/(the hypotenuse=1)). f(x)=Cos(x) maps cosine as a function of the angle.