Review questions 1. A2。 D3.22 4. 13 or 1 19 5. B6。 Isosceles 7.72, 72, 48. 7 9.64 10.8 12.b 13。 Link BC. ab = ac，∴ ABC = ∠ ACB。 And ∫∠Abd =∠ACD, ∴∠ DBC. So OB = OC 16. AB = 10 cm. ∠AED =∠C = RT∞，AE = AC = 6 cm，DE = CD。 Available BE = 4 cm. In Rt△ bed, 42+Cd2 = (8.

3.、 1

3. 1 1. Straight, oblique, rectangular (or square) 2.8,12,6, rectangular 3. Straight pentagonal prisms, 7, 10, 34.b5 (The answer is not unique) For example, they are all straight prisms; There are three edges passing through each vertex; The sides are rectangular. 6. (1) * * has five faces, two bottom faces are triangles with the same shape and area, and three side faces are rectangles with the same shape and area. (2) Nine sides. The total length is (6a+3b) cm7. The number of vertices of a regular polyhedron (v) the number of faces (f) the number of edges (e) v+f-e regular tetrahedron 4462 regular hexahedron 86 122 regular octahedron 68 122 regular dodecahedron 20 12302 regular icosahedron 65438+ 3.6, 74. ( 1) 2 (2) 5.C6。 The surface development diagram is as shown in the figure. Its transverse area is (1? 5+2+2.5)×3 = 18(cm2)； Its surface area is 18+ 12× 1? 5×2×2=2 1 (square centimeter)