Question

PLEASE HELP!

The perimeter of △CDE is 55 cm. A rhombus DMFN is inscribed in this triangle so that vertices M, F, and N lie on the sides CD, CE, and DE respectively. Find CD and DE if CF=8 cm and EF=12 cm.

Answer 1

CD=14

DE=21

Explanation:

ΔCDE is similar to ΔFNE (∠E≅∠E, ∠NFE≅∠DCE) by AA similarity

Using Thales' Intercept Theorem Corollary, you know that:

EN/ED=EF/EC=NF/CD=12/20

Let DN be 8x and NE be 12x

Let NF be 12y and CD be 20y

Then you have a system of equations:

20x+20y+20=55

8x=12y

By solving them, you get y=0.7 and x=1.05⇒

DE=21 and CD=14