# CBSE Class 10-Mathematics: Chapter –7 Coordinate Geometry Part 25

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**Question 21:**

In a classroom, 4 friends are seated at the points and . Champa and Chameli walk into the class and after observing for a few minutes Champa asks Chameli. “Don’t you think ABCD is a square?” Chameli disagrees. Using distance formula, find which of them is correct.

**Answer:**

We have and

Using Distance Formula to find distances AB, BC, CD and DA, we get

Therefore, All the sides of ABCD are equal here. … (1)

Now, we will check the length of its diagonals.

So, Diagonals of ABCD are also equal. … (2)

From (1) and (2), we can definitely say that ABCD is a square.

Therefore, Champa is correct.