What is an isosceles triangle?

An isosceles triangle is defined as a triangle that has at least two sides of equal length. This characteristic allows for certain properties and theorems to apply, such as the fact that the angles opposite the equal sides are also equal. This feature distinguishes isosceles triangles from other types of triangles, such as equilateral triangles (where all sides are equal) and scalene triangles (where all sides have different lengths). Understanding the definition helps in solving various problems in geometry related to triangles, such as those involving congruence, perimeter, and area.