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(3, 1), (–3, 2) and (0, 2 – √3) are the vertices of _____ triangle of area _____.

(a) isosceles; 81 sq. units

(b) scalene; \( \frac{-3+6\sqrt 3 }2\) sq. units

(c) equilateral; 9√3 sq. units

(d) right angled; 81 sq. units

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Best answer

Correct option is (b) scalene; \( \frac{-3+6\sqrt 3 }2\) sq. units

Distance between two points = \(\sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}\)

Distance between the points A(3, 1) and B(−3, 2) = \(\sqrt{(-3-3)^2 + (2 - 1)^2}\)

\(= \sqrt{36 + 1}\)

\(= \sqrt{37}\)

Distance between the points B(−3, 2) and C(0, 2 − √3​) = \(\sqrt{(0+3)^2 + (2 - \sqrt 3 -2)^2}\)

\(=\sqrt {9 + 3}\)

\(= \sqrt {12}\)

Distance between the points A(3, 1) and C(0, 2−√3​)

\(\sqrt{(0-3)^2 + (2 - \sqrt 3 -1)^2}\)

\(=\sqrt {9 +1+ 3-2\sqrt 3}\)

\(= \sqrt {13 - 2\sqrt 3}\)

Since the length of the sides between all vertices are different, they are the vertices of  a scalene triangle. 

Area of △ABC = \(\left|\frac{x_1(y_2 -y_3)+x_2(y_3 - y_1) + x_3(y_1 - y_2)}{2}\right|\)

\(= \left|\frac{3(2 - 2 + \sqrt 3)+ (-3)(2- \sqrt 3 -1) + 0(1 - 2)}{2}\right|\)

\(= \left|\frac{3\sqrt 3 -3+ 3\sqrt 3}2\right|\)

\(= \frac{-3+6\sqrt 3 }2\)

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