improve this sentence: Danielle is correct. An acute isosceles triangle is a triangle with two sides that are equal in length and two acute angles that are equal in measure. In Sasha's statement, the side lengths given are 6 cm, 9 cm, and 12 cm. Since two sides need to be equal for an isosceles triangle, it is not possible for an isosceles triangle to have side lengths of 6 cm, 9 cm, and 12 cm.

Danielle is correct; an acute isosceles triangle consists of two sides that have equal lengths and two acute angles that share the same measure. However, in Sasha's statement, the side lengths specified are 6 cm, 9 cm, and 12 cm. Since an isosceles triangle must have two sides that are equal, it is impossible for an isosceles triangle to have side lengths of 6 cm, 9 cm, and 12 cm.