# Ex.7.1 Q4 Congruence of Triangles - NCERT Maths Class 7

## Question

If \(ΔDEF ≅ ΔBCA\), write the part(s) of \(ΔBCA\) that correspond to

\(\left( \text{i} \right)\,\,\angle E\\\left( \text{ii} \right)\text{ }\overline{EF}~\\\left( \text{iii} \right)\,\,\angle F~\\\left( \text{iv} \right)\overline{\text{ }DF}.\)

## Text Solution

**What is the known?**

Two \( ΔDEF\) and \( ΔBCA\) which are congruent.

**What is the unknown?**

The part(s) of \(ΔBCA\) that correspond to different angles and sides.

**Reasoning:**

This question is based on the concept of congruence of triangles. As it is given in the question two triangles \(DEF\) and \(BCA\) are congruent. We can place triangle \(DEF\) on \(BCA\) such that \(D\) falls on \(B\), \(F\) falls on \(A\), \(F\) falls on \(A\) and \(D\) falls on \(C\).

**Steps:**

Since, \(ΔDEF ≅ ΔBCA\)

For better understanding of this concept it is best to visualize it with the help of figure.

\(\begin{align}&\left( \text{i} \right)\;\;\angle E\leftrightarrow \angle C\\& \left( \text{ii} \right)\;\overline{EF}\leftrightarrow \overline{CA}\\&\left( \text{iii} \right)\angle F\leftrightarrow\angle A \\ & \left( \text{iv} \right)\overline{DF}\leftrightarrow \overline{BA} \\ \end{align}\)