(1) What is a triangle?

A figure surrounded by three line segments is called a triangle.

(2) What sides does a triangle have?

Each line segment forming a triangle is called an edge of the triangle.

(3) What is the vertex of a triangle?

The intersection of every two line segments is called the vertex of a triangle.

(4) What is an acute triangle?

A triangle with three acute angles is called an acute triangle.

(5) What is a right triangle?

A triangle with a right angle is called a right triangle.

(6) What is an obtuse triangle?

A triangle with an obtuse angle is called an obtuse triangle.

(7) What is an isosceles triangle?

A triangle with two equal sides is called an isosceles triangle.

(8) What is the waist of an isosceles triangle?

In an isosceles triangle, two equal sides are called the waist of the isosceles triangle.

(9) What is the vertex of an isosceles triangle?

The intersection of two waists is called the vertex of an isosceles triangle.

(10) What is the base of an isosceles triangle?

In an isosceles triangle, the side that is not equal to the other two sides is called the base of the isosceles triangle.

(1 1) What is the base angle of an isosceles triangle?

The two equal angles on the base are called the base angles of an isosceles triangle.

(12) What is an equilateral triangle?

A triangle with three equilateral sides is called an equilateral triangle, also called a regular triangle.

(13) What is the height of the triangle? What is the base of a triangle?

Draw a vertical line from the vertex of a triangle to its opposite side. The line segment between the vertex and the vertical foot is called the height of the triangle, and the opposite side of the vertex is called the bottom of the triangle.

What is the sum of the internal angles of a triangle (14)?

The sum of the internal angles of a triangle is 180.