To fill in the missing reason for the statement 3, PT ≅ RT, we recognize that T is the midpoint of segment PR due to the definition of a perpendicular bisector.
Given that ST is a perpendicular bisector of PR, we can conclude that point T divides segment PR into two equal segments, PT and RT. Therefore, we can write:
3. PT ≅ RT
Reason: Definition of a midpoint.
The definition of a midpoint states that if T is the midpoint of segment PR, then the segments PT and RT are congruent.