Consider the following triangle. Identify the legs of the triangle. Option (A), line segment 𝐴𝐵 and line segment 𝐵𝐶. Option (B), line segment 𝐴𝐵 and line segment 𝐴𝐶. Or option (C), line segment 𝐵𝐶 and line segment 𝐴𝐶.
Let’s begin by looking at the triangle that has been drawn. Triangle 𝐴𝐵𝐶 has a side 𝐴𝐶 of three centimeters and two shorter sides each of
two centimeters. This means that this must be an isosceles triangle, because by definition an
isosceles triangle has two congruent sides. Line segments 𝐴𝐵 and 𝐵𝐶 are the same length of two centimeters, so we can mark on
the diagram that these are congruent.
This also means that we can identify the legs of this isosceles triangle. The two congruent sides of an isosceles triangle are called the legs of the
triangle. That means that we can give the answer that the two legs of this isosceles triangle
are line segments 𝐴𝐵 and 𝐵𝐶, which was the answer given in option (A).
Although we weren’t asked for it here, the third side of an isosceles triangle is
referred to as the base. Note that this does not have to be the side which is horizontal at the bottom of the
triangle in the way we may typically have seen isosceles triangles drawn. It is simply the noncongruent third side.