What are the functions of sinx and cosx?

The function images of sinx and cosx are shown in the following figure:

Generally speaking, in rectangular coordinate system, given the unit circle, for any angle α, the vertex of the angle α coincides with the origin, the starting edge coincides with the non-negative semi-axis of the X axis, and the ending edge intersects with the unit circle at point P(u, v), so the ordinate V of the point P is called the sine function of the angle α, and it is recorded as v=sinα. Usually, we use X to represent the independent variable, that is, X represents the size of the angle and Y represents the function value, so we define the trigonometric function y=sin x at any angle, and its definition domain is all real numbers, with the value range of [- 1, 1].

Cosine (cosine function), a kind of trigonometric function. In Rt△ABC (right triangle), ∠ C = 90, and ∠A's cosine is the hypotenuse of the adjacent side of the triangle, that is, cosA=b/c, which can also be written as cosa=AC/AB, and cosine function: f(x)=cosx(x∈R).

Symmetry axis and symmetry center:

Y=sinx symmetry axis: x=kπ+π/2(k∈z) symmetry center: (kπ, 0)(k∈z).

Y=cosx symmetry axis: x=kπ(k∈z) symmetry center: (kπ+π/2,0 0) (k ∈ z).

Y=tanx symmetry axis: asymmetry center: (kπ, 0)(k∈z).