If the co-ordinates of the vertices of an equilateral triangle with sides of length ‘a’ are (x1, y1), (x2, y2), (x3, y3), then

The coordinates of the vertices of an equilateral triangle are (x1, y1), (x2, y2), (x3, y3).

So, the area of triangle with given vertices is given by



Given that the length of the sides of an equilateral triangle = a


Also, area of equilateral triangle =



Now, squaring both the sides, we get





Hence Proved


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