Mathematical sine refers to the sine in a right triangle. In a right triangle, the ratio of the opposite side to the hypotenuse of any acute angle ∠A is called the sine of ∠A, which is abbreviated as sinA (from the English word SINE), that is, the opposite side/hypotenuse of SINA = ∠ A.

In ancient times, sine was the ratio of chord to chord. In ancient times, the "string" in "hook, three strands, four strings and five" was the hypotenuse of a right triangle, and "hook" and "strand" were the two right-angled sides of a right triangle. Sine is the ratio of strands to chords, and cosine is the ratio of remaining right angles to chords. Sine = section chief/chord length.

Sine function:

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. X is usually used to represent the independent variable, that is, X represents the size of the angle and Y represents the function value, thus defining the trigonometric function y=sin x of any angle, whose definition domain is all real numbers, and its value range is [- 1, 1].