91Ó°ÊÓ

The angle $∠EFB$consists of two angles which are $∠8$and $∠9$which mean that the addition measurement of these angles will be equal to $∠EFB$.

$∠EFB=∠8+∠9$

Determine the addition of measurement of angles present on the straight line AFE.

$∠10+∠8+∠9=180$

Make an equation by using the angles present in$∠EFB$and the provided property of the angles.

$∠7+∠8+∠9=180$

Compare the obtained equations $∠10+∠8+∠9=180$and $∠7+∠8+∠9=180$$∠7=∠10$.

∠7=∠10

The postulate 10 can be used which states that two angles represents the corresponding angles only when a separate line travels through these two lines which are having a parallel relation between them.

According to the postulate and obtained equal angles the parallel segments are $\stackrel{¯}{CE}$and $\stackrel{¯}{BF}$.