- ARight-angled
- BIsosceles but not equilateral
- CEquilateral
- DScalene
Step-by-Step Solution
Each of △ADF, △BED, △CFE has one side equal to AD, another equal to (side − AD), and a 60° angle between them. By SAS all three are congruent, so DF = ED = FE.
Answer: C) Equilateral