How is the length of the chord related to its distance from the center?

Consider the proof. given: segment ab is parallel to line de. prove: what is the missing statement in step 5?

The fence around a quadrilateral-shaped pasture is 3a^2+15a+9 long. three sides of the fence have the following lengths: 5a, 10a-2, a^2-7. what is the length of the fourth side of the fence?

In the diagram, the ratios of two pairs of corresponding sides are equal to prove that almn - axyz by the sas similarity theorem, it also needs to be shown that x 6 z un z zz un = 2x zləzz lezy