The question asks which side in triangle 2 corresponds to side $a$ in triangle 1. Since the two triangles appear to be similar, corresponding sides can be determined by their relative positions in the triangles.

In triangle 1:

• Side $a$ is opposite to angle $1$.

In triangle 2:

• The side opposite to angle $2$ is side $e$.

Therefore, the side in triangle 2 that corresponds to side $a$ in triangle 1 is side $e$.

Would you like more details on why this is the case, or do you have any questions?

Here are some related questions:

1. What does it mean for two triangles to be similar?
2. How do we identify corresponding angles in similar triangles?
3. What is the significance of corresponding sides in similar triangles?
4. Can similar triangles have different angles?
5. How do you calculate the lengths of unknown sides in similar triangles?

Tip: When dealing with similar triangles, remember that corresponding sides are proportional, and corresponding angles are equal.