Question

vocabulary and core concept check 1. complete the sentence point c is in the interior of ∠def. if ∠dec and ∠cef are congruent, then ec is the ____ of ∠def.

Explanation:

Step1: Recall Angle Bisector Definition

An angle bisector is a ray that divides an angle into two congruent adjacent angles. Here, \( \angle DEC \cong \angle CEF \), and \( C \) is in the interior of \( \angle DEF \), so \( \overrightarrow{EC} \) splits \( \angle DEF \) into two congruent angles.

Step2: Identify the Term

From the definition, a ray that divides an angle into two congruent angles is the angle bisector. So \( \overrightarrow{EC} \) is the angle bisector of \( \angle DEF \).

Answer:

angle bisector