A.
48 B。
60 degrees Celsius.
76 D。
80 7. (Spring of 2014? Golmud City), the three sides of Rt△ABC are expanded to twice the original size, and △ A ′ B ′ C ′ is obtained, then △ A ′ B ′ C ′ is () A. Right triangle B.
Acute triangle C.
Oblique triangle d
Unable to determine
8.(20 12 spring? In Tianmen proofreading, A, B and C are known as three sides of △ABC, with the following conditions: ①a= 12, b=5, C =13; ②a:b:c= 1:
:2; ③a=8，b= 15，c = 17； ④a= 12，b= 1 1，c=5。
Among them, () A can judge that △ABC is a right triangle.
1 B。
Two cs.
Three d's
Four nines. (Autumn 20 12? The three sides of a triangle a, b and c satisfy 2ab=(a+b)2.
﹣c2
Then this triangle is () A.
Oblique triangle B.
Acute triangle C.
Right triangle D.
Equilateral triangle 10. As shown in the figure, all quadrangles in the figure are squares and all triangles are right triangles, where the areas of squares are marked as A, B, C and D respectively, then the relationship between them is ().
A.A+B=C+D B。
A+C=B+D C。
A+D=B+C D。
None of the above is true.
2. Fill in the blanks (*** 10 small questions, 0 for each small question, out of 0) 1 1. (20 1 1? Liaocheng) Simplify:
﹣
= .
12.(20 1 1? Sunshine) It is known that X and Y are real numbers and satisfy =0, then X
20 1 1
﹣
y
20 1 1
= .
Page 3 (***6)
13.(20 1 1? Suizhou) In order to make the formula meaningful, the value range of a is.
14.(20 1 1? Maoming knows that the two square roots of a positive number are 2a ~ 2 and a ~ 4 respectively, so the value of a is.
15.(20 14 spring? In △ABC, ∠ C = 90, if c= 10, A: B = 3: 4, then AB =.
16. (autumn 2009? As shown in the figure, in isosceles △ABC, AB=AC= 10, BC= 12, then the height of AD =.
17. (Autumn 20 14? If the ratio of three sides of a triangle is 5: 12: 13 and its circumference is 60cm, then its area is cm2.
.
18.(20 13? Zhangjiajie) as shown in the figure, OP= 1, if p is PP 1⊥OP, op1=; After P 1, P 1P2⊥OP 1 and
P 1P2= 1，OP2=
; After P2 is P2P3⊥OP2 and P2P3= 1, op3 = 2；; ... continue to follow this rule,
Get op20 12 =.
19.(20 13? Putian is a beautiful pythagorean tree, in which all quadrangles are squares and all triangles are right triangles. If the areas of squares A, B, C and D are 2, 5, 1, 2 respectively, the area of the largest square E is.
Page 4 (***6)
20.(2009? Anshun) The following picture is a schematic diagram of the famous "Zhao Shuangxian Diagram" in ancient China, which is surrounded by four congruent right triangles. If AC=6 and BC=5, extend the right-angled sides of four right-angled triangles with a side length of 6 outward to obtain a "mathematical windmill" as shown in the figure, then the outer circumference of this windmill is.
Third, answer questions (***5 small questions, out of 0) 2 1. Calculation: (1)× calculation
(2)×(﹣
)×(
)
23. (Autumn 20 14? If 3, m and 5 are three sides of a triangle, it is simplified as:
﹣
.
Page 5 (***6)
24.(20 1 1? Sunshine) simplification, evaluation:, where m =.
25.(20 1 1? Taizhou) to solve the equation, and
The value.
26. It is known that x and y are real numbers and y=+2. Find it.
The value.
Fourth, answer the question (***2 small questions, out of 0)
27. (Autumn 20 14? As shown in the figure, the length of equilateral triangle ABC is 6cm, and (1) is the height of AD; (2) Find the area of △ABC.