2. The four sides of the diamond need to be equal, and the lengths of two adjacent sides are actually the lengths of AB and AC of the triangle (equilateral triangle and congruence can be proved, the same as the first step). So as long as AB=AC, that is, the triangle is an isosceles triangle.
Comments on Historical Records 1000 words (1)
For us children who study literature, Historical Records is undoubtedly the most representative maste