Answer:
1. Proportional.
2. ce
3. Segment Addition Postulate.
Step-by-step explanation:
By the angle-angle similarity postulate, △YXZ∼△YZQ and △YXZ∼△ZXQ.
The corresponding sides of two similar triangles are proportional.
Since similar triangles have proportional sides, therefore
and 
Solving the equation for a² and b² gives
and 
The value of a² is cf and the value b² is ce.
Adding these together gives

Factoring out the common segment gives

From the given figure it is clear that
(Segment Addition Postulate)
Using segment Addition Postulate, we get

On simplification, we get

Therefore the required answers are 1. Proportional, 2. ce, 3. Segment Addition Postulate.