Amplitude of a Sine Wave

A graph of the function y( θ ) = c sinθ looks just like the curve in Figure (3), except the curve goes up to a height c and down to –c as shown in Figure (2). We would get the curve of Figure (2) by plotting points around a circle as in Figure (1), but using a circle of radius c. We call this factor c the amplitude of the sine wave. The function sin θ has an amplitude 1, while the sine wave in Figure (2) has an amplitude c (its values range from +c to –c).

Figure 1: The heights ai at various points around a unit circle.

Figure 2: A sine wave of amplitude c.

Figure 3: Several cycles of the curve sin θ .