Nature:
1). The two base angles of an isosceles triangle are equal.
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 (abbreviated as "the three lines of the isosceles triangle are one")?
3) The bisectors of the two base angles of an isosceles triangle are equal.
4) The median vertical line on the bottom of the isosceles triangle is equal to the distance between the two waists.
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)?
7). An isosceles triangle is an axisymmetric figure with only one axis of symmetry. Is the straight line of the bisector of the top angle its symmetry axis?
decision
1). In the same triangle, a triangle with two equal sides is an isosceles triangle (definition)
2). In the same triangle, two triangles with equal angles are isosceles triangles (abbreviation: in the same triangle, the angles are equal and the sides are equal).