The longer the side of an angle, the bigger the angle, right?

No, the size of the angle has nothing to do with the side length of the angle, but if it is within a triangle, the big side is correct for the big angle. For example, if the opposite side A of ∠A is longer than the opposite side B of ∠ B, then ∠A is greater than ∠ B.

A triangle is a closed figure composed of three line segments that are not on the same line. It's called a triangle. Ordinary triangles are divided into ordinary triangles (three sides are not equal) and isosceles triangles (isosceles triangles with unequal waist and equal waist and bottom).

According to the angle, there are right triangle, acute triangle and obtuse triangle, among which acute triangle and obtuse triangle are collectively called oblique triangle.

An isosceles triangle refers to a triangle with two equal sides, which are called the waist of the triangle. In an isosceles triangle, two equal sides are called waist and the other side is called bottom. 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 (abbreviated as "equilateral angles"). The bisector of the vertex, the midline of the bottom and the height of the bottom of an isosceles triangle coincide (referred to as "the three-line unity property of an isosceles triangle").

The bisectors of the two base angles of an isosceles triangle are equal (the median lines of the two waists are equal and the heights of the two waists are equal). The median vertical line on the bottom of the isosceles triangle is equal to the distance between the two waists.