prove that the points (0,0), (5,5), (-5,5) are the vertices of a right angled triangle.

Also,AB^{2} + AC^{2} = 50 + 50 = 100 = 10^{2} = BC^{2}

So, by converse of pythagoras theorem, , given triangle is a right triangle in which, angle A is 90^{0}

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