Consider △ABC in which AB=AC.
(i) Define an isosceles triangle.
(ii) State the relation between the angles opposite the equal sides of an isosceles triangle and justify your statement by referring to congruent triangles.
(iii) If ∠B=58∘, find ∠C.
(iv) Explain why ∠A cannot be equal to ∠B or ∠C in this triangle.