The fourth grade mathematics second volume classroom exercises, answer people's education edition.

(1) Triangle can be divided into three types according to the angle: (acute angle), (right angle) and (obtuse angle).

(2) Triangles are divided by side length, and there are two special types of triangles: (equilateral triangle) and (isosceles triangle).

2. Fill in the brackets with the serial number of the correct answer.

(1) The three internal angles of a triangle are 95, 25 and 60 respectively, and this triangle is (C).

A. acute triangle B. right triangle C. obtuse triangle

(2) Two identical right-angled triangles can be spelled into (C)

A. rectangle B. trapezoid C. parallelogram D. all three are possible

(3) A triangle, which is neither an acute triangle nor a right triangle, will be a triangle (D).

A. positive B. isosceles C. isosceles right angle D. obtuse angle