Question

15 in the triangles shown, what is the reason ( mangle a=mangle d )? sss sas cpctc ( (\triangle abccong\triangle def) ) asa

Explanation:

Step1: Check triangle congruence

If two triangles are congruent, then their corresponding parts (angles and sides) are equal. This is known as CPCTC (Corresponding Parts of Congruent Triangles are Congruent).

Step2: Analyze given markings

The markings on the triangles suggest that $\triangle ABC\cong\triangle DEF$ (assuming the sides and included angles are marked as per congruence criteria). Once we establish $\triangle ABC\cong\triangle DEF$, then $\angle A$ and $\angle D$ are corresponding angles.

Answer:

CPCTC ($\triangle ABC\cong\triangle DEF$)