Which characteristics will prove that ΔDEF is a right, isosceles triangle?

segment DE is larger than segment EF, and their slopes are the same.
segment DE is larger than segment EF, and their slopes are opposite reciprocals.
The lengths of segment DE and segment EF are congruent, and their slopes are the same.
The lengths of segment DE and segment EF are congruent, and their slopes are opposite reciprocals.

Question

Which characteristics will prove that ΔDEF is a right, isosceles triangle?

segment DE is larger than segment EF, and their slopes are the same.
 segment DE is larger than segment EF, and their slopes are opposite reciprocals.
 The lengths of segment DE and segment EF are congruent, and their slopes are the same.
 The lengths of segment DE and segment EF are congruent, and their slopes are opposite reciprocals.

Vocaloid · Answer

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Vocaloid · Answer

thoughts? right off the bat DE and EF have to be congruent if this is isosceles

if they make a right angle are their slopes equal or opposite reciprocals?