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:

Prove that A(4, 3), B(6, 4), C(5, 6), D(3, 5) are the vertices of a square ABCD.

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 = \sqrt{(6 - 4)^2 + (4 - 3)^2} = \sqrt{(4 + 1)} = √5

BC = \sqrt{(5 - 6)^2 + (6 - 4)^2} = \sqrt{(1 + 4)}  = √5

CD = \sqrt{(3 - 5)^2 + (5 - 6)^2} = \sqrt{(4 + 1)}  = √5

and AD = \sqrt{(3 - 4)^2 + (5 - 3)^2} = \sqrt{(1 + 4)}  = √5

Since, AB = AC = BC = AD, hence our 1st condition is verified.

Step 3: Let’s check for diagonals now:

∴ AC = \sqrt{(5 - 4)^2 + (6 - 3)^2} = \sqrt{(1 + 9)}  = √10

and BD = \sqrt{(3 - 6)^2 + (5 - 4)^2} = \sqrt{(9 + 1)}  = √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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