The parent functions of sine and cosine functions are $y=\sin (x)$ and $y=\cos (x),$ respectively. Thus, it is important to know how their graphs look and some of their characteristics. Graphing them is done by first evaluating some inputs and obtaining their corresponding outputs using a table. Here, radians will be used, but the functions can be evaluated for degrees as well.

Plotting these points and connecting them with smooth curves gives the graphs.

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Both functions have the amplitude $1,$ which is half the difference between the greatest and least function values. These functions are both periodic, as they have a repeating pattern. The smallest repeating part of the graph is called a cycle. The horizontal length of the cycles is called the function's period, which is $2\pi$ for both $y=\sin (x)$ and $y=\cos (x).$