A. line segment B. isosceles triangle C. right triangle D. circle

2. If the two sides of an isosceles triangle are 4 and 9 respectively, the circumference is ().

17b.22c.13d.17 or 22

3. If the height of one side of a triangle bisects the angle opposite to this side, then the triangle must be ().

A. isosceles triangle B. right triangle C. equilateral triangle D. isosceles right triangle

4. Xiao Ming put two congruent right-angled triangles with an included angle of 60 into a graph as shown in the figure, in which two longer right-angled sides are on the same straight line, then the number of isosceles triangles in the figure is ().

A.4B.3C.2D. 1

5. As shown in the figure, it is known that △ABC, ∠ ABC = 90, ∠ A = 30, BD⊥AC, DE⊥BC, D and E are vertical feet, and the following conclusion is correct ().

A.AC=2ABB。 AC=8ECC。 CE=BDD。 BC=2BD

6. There are four triangles that meet the following conditions: (1) One angle is equal to the sum of the other two internal angles; (2) The ratio of the three internal angles is 3: 4: 5; (3) The trilateral ratio is 5:12:13; (4) The lengths of the three sides are 5, 24 and 25 respectively. Among them, the right triangle has ().

1。

7. As shown in the figure, EA⊥AB, BC⊥AB, AB=AE=2BC, D is the midpoint of AB, and the following judgments are made: ① DE = AC; ②de⊥ac； ③∠CAB = 30； ④∠EAF=∠ADE。 The number of correct conclusions is ()

A. 1B.2C.3D.4

8. As shown in the figure, an isosceles right triangle with two vertices A and B can be made into ().

A.2 B.4 C.6 D.8

9. As shown in the figure, it is known that in △ABC, AB=6, AC=9, AD⊥BC is at any point of D, and M is AD, then MC2=MB2 is equal to ().

A.9B.35C.45D cannot be calculated.

10. If △ABC is two right-angled triangles with right-angled sides of 5 and 12 respectively, and there is a point D in the triangle, then the distance from D to △ABC is equal, then this distance is equal to ().

A.2B.3C.4D.5