Draw a triangle. How many sides does a triangle have? How many angles? How many vertices? And write it on the triangle.

A triangle has three sides, three angles and three vertices.

A closed figure composed of three line segments that are not on the same straight line is called a triangle. A figure surrounded by three straight lines on a plane or three arcs on a sphere is called a plane triangle;

A figure surrounded by three arcs is called a spherical triangle, also known as a triangle. A closed geometry consisting of three line segments connected end to end is called a triangle. Triangle is the basic figure of geometric figure.

Extended data:

Classify triangle types by angle:

Judgment method 1:

1, acute triangle: all three internal angles of the triangle are less than 90 degrees.

2. Right triangle: One of the three internal angles of the triangle is equal to 90 degrees, which can be recorded as Rt△.

3. obtuse triangle: one of the three internal angles of the triangle is greater than 90 degrees.

Decision method 2:

1, acute triangle: the largest of the three internal angles of a triangle is less than 90 degrees.

2. Right triangle: The largest of the three internal angles of a triangle is equal to 90 degrees.

3. obtuse triangle: the largest of the three internal angles of a triangle is greater than 90 degrees and less than 180 degrees.

Among them, acute triangle and obtuse triangle are collectively called oblique triangle.