AB is congruent to DE because segment DE was constructed so that DE = AB. BC is congruent to EF because segment EF was constructed so that EF = BC. Since ADEF is a right triangle, DE+ EF? = DF? by the We are given that AB + BC2 = AC? Since DE = AB and EF = BC, DE2 + EF2 = AC? by the Also, DF2 = AC2 by the Taking the square root of both sides of the equation gives DF = AC. So, AC is congruent to DF by the definition of congruence. Applying the AABC - ADEF. By CPCTC, ZB _ZE. Therefore ZB is a right angle and AABC is a right triangle.