 Hi and welcome to the session. I am Deepika here. Let's discuss the question. In a classroom four friends are seated at the points A, B, C and D as shown in the figure. A, B, C, D these are the four friends. Champa and Jamili walk into the class and after observing for a few minutes, Champa asks Jamili, don't you think ABCD is a square? Jamili disagrees. Using distance formula, find which of them is a correct. Now before solving this question, let us recall the definition of square. A quadrilateral is a square if it's all sides are equal and diagonals are also equal. So let's start the solution. Now b is the coordinates of the coordinates of dr. Now by using the distance formula, 12 to c square plus 7 minus 4 square which is equal to this is equal to root 18. Now distance bc is equal to 6 square plus 4 minus 7 square which is again equal to 9 plus 9 which is equal to 18 and distance cd is equal to minus 9 square plus 4 square equal to 9 is equal to minus 9 square c square plus 1 minus 4 square this is equal to 9 which is equal to 18 equal to which is equal to 6 which is again equal to 6. 2 distance bc which is again equal to cd distance bc is root 18 this is cd is root 18 and dA is root 18 and also champa is correct because champa said abc disagrees a square so it means she is correct. This is our answer for the above question. I hope the question is clear to you.