Exercise 43 Page 557

Let's recall the definition of similar polygons. Two polygons are similar if and only if their corresponding angles are congruent and corresponding side lengths are proportional. Notice that not all of the pairs of isosceles triangles satisfy the above conditions. However, we can find pairs of isosceles triangles with congruent corresponding angles and proportional corresponding side lengths. Therefore, two isosceles triangles are sometimes similar polygons.