Question 1195477
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Yes, they are.   

Square of the distance between first two points:
{{{ (3-3)^2 + (5-3)^2 = 4 }}}

Sum of squares of distances between 1st & 3rd and  2nd & 3rd points: 
{{{ ((3-2)^2 + (5-4)^2) + ((3-2)^2 + (3-4)^2) = (1 + 1) + (1 + 1) = 4  }}}

So the triangle is a right triangle (with the right angle at (2,4))