2. If there is a cone volume and surface area in the multiple-choice question, directly look at the option area, and find the small one with a difference of 2 times is the answer, and the small one with a difference of 3 times is the answer. I have been trying!
3. The second problem of trigonometric function, such as finding the first boundary angle such as a(cosB+cosC)/(b+c)coA, and then taking the angle A calculated in the first problem as 60 degrees, directly assuming that both B and C are equal to 60 degrees to enter the solution. Save time and effort!
4. There is a step in the process of proving space geometry that I really can't think of directly writing unused conditions and then drawing unexpected conclusions. If the first question really can't be written directly, the second question can be used directly! Students who use conventional methods suggest that a spatial coordinate system should be established at will first. If you make a mistake, you can get 2 points!
5, the second question of solid geometry tells you to find the cosine value, generally using the coordinate method! If you find the angle, the conventional method is simple!
6, multiple-choice questions, the relationship between line and surface can be seen from item D first, which is a waste of your time.
7. Directly observe the range of values in multiple-choice questions. Taking a special point from each option that is different from other options is the answer that can be established.
8. The linear programming problem directly finds the intersection point and brings it into the comparison size.
9. In the case of options A. 1/2, B. 1, C.3/2 and D.5/2, the answer is generally D, because B can be regarded as 2/2, and the first three are all made up by the questioner. If the answer is in the first three, D should be 2(4/2).