I checked the answer of Sina Education again, which is also Wenhai's, but it has been changed to π. I think the correct answer should be π. Here, by the way, the so-called real questions on the Internet, I saw Du Wen's real questions. The first problem of 17 is to find the equation of revolution surface, but their real problems are all written as ellipsoid area s 1 and cone area s2. I can't figure it out after thinking for a long time. The formulas of spherical surface area and conical surface area have long been forgotten in high school, but later the area formula was discovered. I can't remember how to find it in high school. 19 is also copied wrong, and the brackets under the semicolon omit the Z plane. Later, I compared the answers to other questions and found that they mistyped the stem and added the word "product". After knowing this, I really want to swear. []