Graph of trigonometric functions definition is – a function of an arc or angle most simply expressed in terms of the ratios of pairs of sides of a right-angled triangle —called also circular function.
standard unit circle (a circle with radius 1 unit), starting at the origin and making some angle with the x -axis, the sine of the angle gives the y -component.
Due to periodicity in nature of sin and cos function. Therefore we use for graph of waves
Graphs of Trig Functions