Q) Prove that A(4, 3), B(6, 4), C(5, 6), D(3, 5) are the vertices of a square ABCD.
Ans: Let’s plot the points on the graph:

Step 1: Now for a quadrilateral ABCD to be a square, required conditions are:
i) its all four sides should be equal i.e. AB = BC = CD = AD
ii) its diagonals should be equal i.e. AC = BD
Step 2: Let’s calculate the lengths of each of the three sides:
We know that the distance between two points (X1, Y1) and (X2, Y2) is given by:
S = √ (X2 – X1)2 + (Y2 – Y1)2 )
∴ AB =
= √5
BC =
= √5
CD =
= √5
and AD =
= √5
Since, AB = AC = BC = AD, hence our 1st condition is verified.
Step 3: Let’s check for diagonals now:
∴ AC =
= √10
and BD =
= √10
Since, AC = BD, hence our 2nd condition is also verified.
Hence, quadrilateral ABCD is a square.
Therefore, the given 4 points re vertices of a square ABCD.
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