Answer:
Question 11:
∠ABC = ∠EDC = 90° (given)
∠ACB = ∠ECD (vertically opposite angles)
∴ Triangle ABC is similar to triangle ECD. (AA Similarity Test)
Question 12:
Since triangles ABC and ECD are similar,
=
=
![(9)/(DE)](https://img.qammunity.org/2023/formulas/mathematics/college/bnauo26lrcjztyi54d7ff40ulser84vjla.png)
∴ DE = 9 ÷
![(13.5)/(22.5)](https://img.qammunity.org/2023/formulas/mathematics/college/fbt2bfhcp2p8b0mpo278emxylo1ntijjzz.png)
= 15cm
∴ The length of DE is 15cm.