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人教版九年义务教育课本《几何》第三册第180页有一例:“已知正三角形的边长为a,求它的内切圆和外接圆组成的圆环的面积.”本题答案是s=πa2/4.由该例可引申出一系列问题: 题1 已知正三角形的边长为a,则它的外接圆与内切圆的面
There is an example on the 180th page of the third edition of the textbook “Geometry” in the nine-year compulsory education textbook of People’s Education Press. “The area of the circle that is formed by the inscribed circle and the circumscribed circle of the known equilateral triangle is a.” The answer to this question is s=πa2/4. A series of problems can be derived from this example: Question 1 The length of the side of a known regular triangle is a, then its circumscribed circle and inscribed circle face