Kasey and Emma are examining the triangles formed by a diagonal of a rectangle.

Kasey believes a diagonal will always partition a rectangle into two right triangles. Her reasoning is that since every rectangle has four right angles, each triangle formed by the diagonals will have a right angle.

Emma believes a diagonal will always partition a rectangle into two congruent triangles. Her reasoning is that since the diagonal acts as a transversal between parallel lines, the ASA criterion is satisfied by the diagonal and the two angles formed by the transversal.

Whose reasoning is valid?