Fill in the blanks. (65438+ 0 points per grid, 20 points)

1. Triangle has () sides, () angles and () vertices.

2. A triangle has at most () acute angles, () right angles and () obtuse angles.

3. In a triangle, ∠ 1 = 45, ∠ 2 = 65, ∠ 3 = ().

4.∠ 1 and ∠2 are two acute angles of a right triangle, ∠ 1 = 36, ∠ 2 = ().

5. If the base angle of an isosceles triangle is 35, then its vertex angle is (); If its top angle is 102, then its bottom angle is ().

6. One side of an equilateral triangle is 6 cm long and its circumference is () cm.

7. The base length of an isosceles triangle is 12cm, the waist length is 15cm, and the circumference is () cm.

8. A triangle with a perimeter of 15cm may have three sides with lengths of () cm, () cm and () cm respectively.

9. The minimum internal angle of a triangle is 60, and this triangle must be a () triangle; If the sum of two internal angles in a triangle is equal to the other internal angle, then it is a triangle.

10. Count, there are () acute triangles, () obtuse triangles and () right triangles in the figure.

Second, judge. (16)

1. An equilateral triangle is also an isosceles triangle. ( )

2. In an obtuse triangle, there is only one obtuse angle. ( )

A triangle has two acute angles. This triangle is an acute triangle. ( )

4. An obtuse triangle has only one height. ( )

5. An equilateral triangle must be an acute triangle. ( )

6. Put two triangles together to form a big triangle, and the sum of the inner angles of this big triangle is 360. ( )

7. An isosceles triangle with an angle of 60 must be an equilateral triangle. ( )

The three sticks of 8.2 cm, 2 cm, 1 1 cm can form an isosceles triangle. ( )

Third, multiple choice questions. (Choose the serial number of the correct answer and fill in the brackets) (12 points)

The sticks in the 1. () group can form a triangle.

① 2cm、4cm、6cm ② 3cm、5cm、4cm。

③ 3cm, 5cm,10cm.

2. () The three triangles below are obtuse triangles.

① ② ③

3. In a triangle, ∠ 1 = 54, ∠ 2 = 38, this triangle is a () triangle.

① acute angle ② obtuse angle ③ right angle

4. Divide the 12cm stick into three sections to form an isosceles triangle. The following statement is correct ().

①3 cm, 4 cm, 5 cm, 28 cm, 2 cm, 2 cm.

③2 cm, 5 cm, 5 cm

5. Two identical () triangles can form a square.

① acute angle ② right angle ③ isosceles right angle

6. A triangle is both a right triangle and an isosceles triangle, and one of the angles is 45.

① Possibility ② Not necessarily ③ certainty.

Fourth, the operation questions. (24 points)

1. Draw a line segment in each diagram as required. (4 points)

Divided into two obtuse triangles and two acute triangles.

2. Draw the height at the bottom of each triangle. (6 points)

3.( 1) Divide the graph 1 into right triangles and obtuse triangles. (2 points)

(2) Divide Figure 2 into right triangle and acute triangle. (2 points)

Figure 1 Figure 2

(1) A small ant wants to climb from point A to point C, and the shortest crawling distance is close to () cm. (2 points) (2) This little ant wants to climb from point A to the opposite BC. What is the shortest route to crawl? Draw with a brush. (2 points)

5. Draw triangles on the grid as needed. (6 points)

(1) Draw a triangle, which is both an isosceles triangle and a right triangle.

(2) Draw a triangle, which is both an isosceles triangle and an acute triangle.

(3) Draw a triangle, which is both an isosceles triangle and an obtuse triangle.

Fifth, solve the problem. (28 points)

1. Use a rope with a length of 150 cm to form an equilateral triangle. How long is each side of this equilateral triangle?

2. The two adjacent sides of an isosceles right triangle are 8m and 5m respectively. What's its circumference?

What is the circumference of an isosceles triangle surrounded by strips of 3.20 decimeters and 50 decimeters?

The top angle of isosceles triangle is half of the bottom angle. What are the top and bottom angles of this triangle?

5. equilateral triangles and squares have equal perimeters. The side length of a square is 12 cm. What is the side length of an equilateral triangle?

6. A regular triangular flower bed was built in the happy community, and 15 pots of chrysanthemums were placed on both sides of the flower bed (one pot at each vertex). How many pots are put in a * * *?

7. The two straight lines A and B in the picture below are parallel to each other. Are the heights on the bottom sides of the following four triangles equal in length? Why?