In the images of 1 and sine function y=sinx, x ∈ [0 0,2π], the five key points are: (0,0) (π/2, 1) (π, 0)(3π/2,-1.

2. Trigonometric function plays an important role in studying the properties of geometric shapes such as triangles and circles, and it is also a basic mathematical tool for studying periodic phenomena. In mathematical analysis, trigonometric function is also defined as the solution of infinite series or specific differential equation, which allows its value to be extended to any real value or even complex value.

3. Trigonometric function is one of the common and important test sites in college entrance examination, and it belongs to basic elementary function. Common trigonometric functions are sine function, cosine function and tangent function.

4. There are some special angles, such as 30, 45 and 60. The trigonometric functions of these angles are simple monomials, and the specific values can be obtained directly in the calculation.

5. The domain of sin (x) and cos (x) is R, and the range of values is [- 1,1]; The definition domain of tan(x) is that x is not equal to π/2+kπ, and the value domain is r.