Since it is given that ab ≅ ac, it must also be true that ab = ac. assume ∠b and ∠c are not congruent. then the measure of one angle is greater than the other. if m∠b > m∠c, then ac > ab because of the triangle parts relationship theorem. for the same reason, if m∠b < m∠c, then ac < ab. this is a contradiction to what is given. therefore, it can be concluded that ab ≠ ac ∠b ≅ ∠c abc is not a triangle ∠a ≅ ∠b ≅ ∠c