Answer the following with reference to congruent triangles.
(i) Define congruent triangles.
(ii) State the rule under which two right-angled triangles are congruent when their hypotenuse and one corresponding side are equal.
(iii) Draw and neatly label two right-angled triangles that satisfy the above rule. Mark all the equal parts on your sketch.
(iv) Explain briefly why knowing only the hypotenuse and one side is not sufficient to establish congruence of two obtuse-angled triangles.