Which side of DEF is the longest?
A. DE
B. EF
C. DF
D. Cannot be determined

Option (A) DE side of the triangle DEF is the longest side.
A triangle is a flat geometric figure that has three sides and three angles. The sum of the interior angles of a triangle is equal to 180°. The exterior angles sum up to 360°.
For the given situation,
The diagram shows the triangle with angles ∠D = 65°, ∠E = 42°.
The sum of the interior angles of a triangle is equal to 180°.
⇒ [tex]\angle D+\angle E+\angle F=180[/tex]
⇒ [tex]65+42+ \angle F=180[/tex]
⇒ [tex]\angle F=180-107[/tex]
⇒ [tex]\angle F=73[/tex]
The side corresponding to the ∠D is EF, ∠E is DF, ∠F is DE
The angle which is greater has the longest side.
⇒ [tex]\angle F > \angle D > \angle E[/tex]
⇒ [tex]DE > EF > DF[/tex]
Thus the side DE has the longest length.
Hence we can conclude that option (A) DE side of the triangle DEF is the longest side.
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