The trigonometric function values of common angles are 30, 45 and 60. The sine and cosine values of these three angles have one thing in common: the denominator is 2, and if the numerator adds a root sign, the root sign will correspondingly become 1, 2, 3.

Trigonometric function is a kind of transcendental function in elementary function in mathematics. Their essence is the mapping between the set of arbitrary angles and a set of ratio variables. The usual trigonometric function is defined in the plane rectangular coordinate system, and its domain is the whole real number domain. The other is defined in a right triangle, but it is incomplete.

About function:

The definition of function is usually divided into traditional definition and modern definition. The two definitions of functions are essentially the same, but the starting point of describing concepts is different. The traditional definition is from the perspective of movement change, and the modern definition is from the perspective of set and mapping.