An equilateral triangle.

Symmetry axis A straight line that makes a geometric figure symmetrical or rotationally symmetrical. One part of a symmetrical figure rotates around it for a certain angle and then coincides with another part.

Many figures have axes of symmetry. For example, an ellipse or hyperbola has two axes of symmetry and a parabola has one axis of symmetry.

Extended data:

Nature:

1, the number of two base angles of an isosceles triangle is equal (referred to as "equilateral equilateral angle").

2. The bisector of the top angle of the isosceles triangle, the median line on the bottom edge and the height on the bottom edge coincide (referred to as "isosceles triangle with three lines in one").

3. The bisectors of the two bottom angles of the isosceles triangle are equal (the midline of the two waists is equal and the height of the two waists is equal).

4. The distance from the perpendicular to the bottom of the isosceles triangle to the waist is equal.

5. The included angle between the height of one waist and the bottom of an isosceles triangle is equal to half of the top angle.

6. The sum of the distances from any point on the bottom of an isosceles triangle to two waists is equal to the height of one waist (proved by equal area method).

Expand:

An isosceles triangle is a triangle with at least two equilateral sides. IsoscelesTriangle refers to a triangle with at least two equilateral sides, which is a special term in mathematics. It is defined as an isosceles triangle. The two equal sides of an isosceles triangle are called the waist and the other side is called the bottom.

Definition of isosceles triangle:

The angle between the two waists is called the top angle, and the angle between the waist and the bottom edge is called the bottom angle. The two base angles of an isosceles triangle are equal, which is abbreviated as equilateral corner. An isosceles triangle is not only an axisymmetric figure, but also consists of two congruent triangles. An isosceles triangle can be easily obtained by folding paper-cutting.

An isosceles triangle has the properties of equilateral, equilateral and the unity of three lines. It has important applications in the calculation and proof of plane geometry and geometric optics in physics. A triangle with two equilateral sides is called an isosceles triangle, in which two equilateral sides are called the waist of the isosceles triangle, and the other is called the angle between the waist of the bottom side is called the vertex.