17, trigonometric function, mainly sine and cosine theorem, and the application of trigonometric formula. Or the number sequence problem, examine arithmetic, and the arithmetic ratio is simple and applicable. 17 generally has two problems. 18 belongs to application problems, probability statistics, histograms, distribution tables, expectations and other applications. 19, solid geometry, determination of spatial position relationship, and calculation of spatial angle and distance. 20. Analytic geometry, find the positional relationship between straight line and conic curve of trajectory equation (conic curve) and its application, and investigate the thought and application of function and equation. 2 1, function problem, investigation, application of derivative in learning function, classification transformation, classification discussion and other mathematical ideas. 22. Selected lectures on geometric proof, examining the relationship between straight line and circle position, and similar proportional line segments. Polar coordinate parametric equation, polar coordinate, or parametric equation, simple application. 24. Inequality proofs are generally absolute inequalities, functions and images.