Name the quadrilateral ABCD, the coordinates of whose vertices are A(3, 5), B(1, 1), C(5, 3) and D(7, 7). -Maths 9th

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Answer :

(b) Equilateral, \(2\sqrt3a^2\) sq. unitsLet A(a, a), B(–a, –a) and C \((-\sqrt3a,\sqrt3a)\) be the vertices of ΔABC. Then,AB = \(\sqrt{(a+a)^2+(a+a)^2}\) = \(\sqrt{4a^2+4a^2}\) = \(\sqrt{8a^2}\) = \(2\sqrt2a\)BC = \(\sqrt{(-a+\sqrt3a)^2+(-a-\sqrt3a)^2}\)= \(\sqrt{a^2-2\sqrt3a+3a^2+a^2+2\sqrt3a+3a^2}\) = \(\sqrt{8a^2}\) = \(2\sqrt2a\)AC = \(\sqrt{(-a+\sqrt3a)^2+(-a-\sqrt3a)^2}\)= \(\sqrt{a^2+2\sqrt3a+3a^2+a^2-2\sqrt3a+3a^2}\) = \(\sqrt{8a^2}\) = \(2\sqrt2a\)∵ AB = BC = AC, ΔABC is equilateral.Area = \(rac{\sqrt3}{4}\) (side)2 = \(rac{\sqrt3}{4}\) x (\(2\sqrt2a\))2= \(rac{\sqrt3}{4}\) x 8a2 = \(2\sqrt3a^2\).

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