The sine function is one of the three primary functions in trigonometry, nthe others being cosine and tan functions.

The sine x or sine theta can be defined as the ratio of the opposite side of a right triangle to its hypotenuse.

and

Cos function (or cosine function) in a triangle is the ratio of the adjacent side to that of the hypotenuse.

The cosine function is one of the three main primary trigonometric functions and it is itself the complement of sine(\(\cos+\sin e\)).

The domain of a function is the set of all possible inputs for the function.

For example:

the domain of \(\displaystyle{f{{\left({x}\right)}}}={x}^{{2}}\) is all real numbers, and the domain of \(\displaystyle{g{{\left({x}\right)}}}=\frac{{1}}{{x}}\) is all real numbers except for \(x=0\).

The two trigonometric functions defined for all real numbers are the sine function and the cosine function. The domain of each of these functions is\(\displaystyle{\left(−\infty,\infty\right)}\).