The cycle and frequency
Wavelength is the distance between one cycle of a wave. Frequency is the number of complete cycles in one second. The period of a wave is the time taken for one complete cycle. Period = 1 / frequency. Frequency = 1 / period. [ Hz ]
Sine wave 
The Unit Circle is a circle with a radius of 1.
The diagram shows one cycle of a sine wave.
The sine of the angle θ is represented by the y-value of the point on the unit circle.
Sine wave animation(HTML5) white：radius = 1 green：sinθ red：The location on radius r when being angle θ blue：additional line
