(A) -3 (B)-5 (C)-7 (D) - 15

2. The following statement is correct (C)

A. All isosceles triangles are similar. All right-angled triangles are similar.

C. All isosceles right triangles are similar. Two isosceles triangles with equal angles are similar.

3. If two golden section points P and Q are found on the line segment with the length of 1, PQ = (0.236).

Answer. The fourth century BC.

4. As shown in figure ∠ APD = 90, AP = Pb = BC = CD, then the following conclusion holds (without the figure, it can't be done).

a .δPAB∽δPCA b .δPAB∽δPDA

c .δABC≈δDBA d .δABC≈δDCA

5. If it is known, its value is (impossible! )

A. 2 D BC.

6. It is known that three sides of ABC are 0, 2, and two sides of Δ A ′ B ′ C ′ are 1. If ABC is similar to Δ a ′ b ′ c ′, then the third side of Δ a ′ b ′ c ′ should be (insufficient condition! )

A.B. C. D。

7. As shown in the figure, AB is a long ladder against the wall, the ladder foot B is 1.6m away from the foot of the wall, the point D on the ladder is 1.4m away from the wall BD, and the length of the ladder is 0.55m.

3.85m high, 4.00m low, 4.40m high and 4.50m high.

8. As shown in figure ∠ ACB = ∠ ADC = 90, BC = A, AC = B, AB = C. To make ∠? ABC ∽? CAD, as long as CD is equal to (c/b 2).

A.B. C. D。

9. In △ABC and △, the following conditions are met: ①; ⑵

③∠A =∞； (4) ∠ c =∞. If you choose any two conditions to form a group, you can judge.

△ABC∽△ * * Yes (? ) group.

a、 1 B、2 C、3 D、4

10. The similarity ratio of two similar triangles is 2: 3, in which the area of the smaller triangle is 12 and the area of the other triangle is (d).

(A)8 (B) 16 (C)24 (D)27

2. Fill in the blanks (2 points for each small question, 20 points for * * *)

1. If x: y = 3, then x: (x: (x+y) = _ 3: 4 _ _ _ _ _

2. It is known that CD is the height on the hypotenuse AB of RT δ ABC, and AC = 6 cm, BC = 8 cm, then CD = _ 4.8 cm _ _ _

3. The area ratio of two similar triangles is 4: 9, so their perimeter ratio is _ _ 2: 3 _ _.

4. The side ratio of a triangle is 2: 5: 6, and the largest side of another triangle similar to it is 24, and the smallest side is _ _ _ _ _.

5. The length of the part drawn on the drawing with the scale of 1: 20 is 32mm, and the actual length of the part is _ _ 640 mm _ _

6. Xiaoying measured the shadow length of 2m-high benchmark in the sun as 1.2m, and measured the shadow length of a tree as 3.6m and the height of the tree as __6m__.

7. Fold a rectangular piece of paper in half. If the folded rectangle is similar to the original rectangle, the length-width ratio of the original rectangular paper is _1.414:1(root number 2: 1) _ _

8. If, then k=

9. Connect the midpoints of the three sides of the triangle in turn, and the ratio of the midline of the triangle to the corresponding side of the original triangle is 1: 2.

10. In triangle ABC, D and E are the midpoint of AB and AC respectively, so the ratio of triangle ADE to quadrilateral DEBC area is 1: 3.