Which statement proves that triangle XYZ is an isosceles right triangle?

An isosceles right triangle must have two equal sides that meet at a right angle. In choice C, XZ and XY are both 5, so the triangle is isosceles. Their slopes are 3/4 and −4/3, which are negative reciprocals; therefore, those segments are perpendicular and meet at a right angle. Choice D establishes equal sides but does not establish a right angle.

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