题目

What leads to success in school? 【1】 “Perseverance” for example, seems to be a better predictor of success than IQ in school and beyond. Researchers have also demonstrated that having a “growth mindset” is associated with academic success which happens when a person recognizes that abilities are not fixed but developed through practice.Researchers are exploring other characters that might contribute to success. 【2】 Data was collected on happiness and grades from 435 students at St Andrew’s including elementary, middle and upper school students.【3】 Specifically, researcher在如图所示的几何体中，四边形是等腰梯形，∥，平面.（Ⅰ）求证：平面；（Ⅱ）求二面角的余弦值.