Sine and cosine

A trig function is the function of an angle and relate to the angles of a triangle to the length of its sides. Sine is the trigonometric function that is equal to the ratio of the side opposite of a given angle to the hypotenuse in a right triangle. Cosine is the trigonometric function that is equal to the ratio of the adjacent side to the hypotenuse of a given angle in a right triangle. The ratios can be easily remembered through the acronym SOH-CAH -TOA. The first letters of each group stands for the trig function (sin, cosine, or tangent). The two letters following represent the ratios. So Sin(Opposite/Hypotenuse)=SOH and so on. 

The graph of sine begins at the origin while the graph for cosine begins at 1 or your amplitude.