Prove that the points A (1, 7), B (4, 2), C (-1, -1) and D (-4, 4) are the vertices of a square.
Vertices of a square ABCD are: A (1, 7), B (4, 2), C (-1, -1) and D (-4, 4) Length of side AB =
Length of side AB = = = units
Length of side BC = = = units
Length of side CD = = = units
Length of side DA = = = units
Length of diagonal BD = = = units
Length of diagonal AC = = = units
Since opposite sides are equal and diagonal are equal. Therefore given vertices are the vertices of a square.