The incenter of the triangle D and the length of the segment DE of 3 cm, indicates that the length of the segment DF is 3 cm
The steps used to find the length of the segment DF are as follows;
The incenter of a triangle is the center of an inscribed circle of the triangle
The definition of the incenter of a triangle indicates that the perpendicular segments from the incenter to the sides of the triangle are congruent, therefore;
DE = DF, DE = DG, and DF = DG
DE = 3 cm, therefore DF = 3 cm
Please find attached the possible triangle ΔABC in the question, obtained from a similar question found through search