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题1 如图1,四边形 AEFG与ABCD都是正方形, 它们的边长分别为a,b(b≥ 2a),且点F在AD上(以下问题的结果用a,b的代数式表示)． (1)求S△DBF; (2)把正方形AEFG绕点A按逆时针方向旋转45°
Problem 1 As shown in Figure 1, the quadrilaterals AEFG and ABCD are squares, their side lengths are a and b (b≥2a), and the point F is on AD (the result of the following problem is represented by the algebraic expression of a and b). (1) Find SΔDBF; (2) Rotate the square AEFG around point A counterclockwise by 45°