Triangle Side Identification: Is BC a Side in the Given Triangles?

Let's solve the problem step-by-step.

• We first consider the two triangles given in the diagram. The vertices of the first triangle are labeled $A$, $B$, and $C$. The vertices of the second triangle are labeled $D$, $E$, and $F$.
• Identify the sides of the first triangle: Since the vertices are $A$, $B$, and $C$, the sides of the triangle are $AB$, $BC$, and $CA$.
• Identify the sides of the second triangle: With vertices $D$, $E$, and $F$, the sides are $DE$, $EF$, and $FD$.
• Now, we ascertain whether $BC$ is a side. Upon inspection, $BC$ is clearly the side connecting vertex $B$ and vertex $C$ in the first triangle.

Thus, we conclude that Yes, $BC$ is indeed a side of one of the triangles.

The solution to the problem is: Yes