First, the relationship formula:
1. Suppose the ratio of the three sides of a triangle is A, B and C, and the corresponding angles are A, B and C respectively. The angular relation formula with trigonometric function is sine function sinA=a/h, cosine function cosA=b/h, tangent function tanA=a/b, cotangent function cotA=b/a, seca).
2. Assuming that the coordinates of point A are (x, y), the length of the line segment from the origin to point A is r, and the included angle between the line segment R and the abscissa is α, then the angular relationship formula with trigonometric function is sinα=y/r, cosα=x/r, tanα=y/x, cotα=x/y, and sec α = r/x..
Second, the trigonometric function is introduced:
1, trigonometric function is one of the basic elementary functions. It takes the angle as the independent variable, and the angle corresponds to the coordinates of the intersection of the terminal edge of any angle and the unit circle or its ratio as the dependent variable.
2. Trigonometric functions can also be defined by the lengths of various line segments related to the unit circle. Trigonometric function plays an important role in studying the properties of geometric shapes such as triangles and circles, and is also a basic mathematical tool for studying periodic phenomena.
3. In mathematical analysis, trigonometric function is also defined as the solution of infinite series or specific differential equation, allowing its value to be extended to any real value or even complex value.