Prove that the points (0, 0), (5, 5) and (-5, 5) are the vertices of a right isosceles triangle.
Vertices of a quadrilateral are A (0, 0), B(5, 5) and C(-5, 5)
Using distance formula =
AB = 
= 
= 
units
BC = 
= 
= 
units
CA = 
= 
= 
units
Since AB = CA
Using Pythagoras theorem
BC2 = AC2 + AB2
100 = 50 + 50
100 = 100
Therefore vertices are of right isosceles triangle.
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