Question

1. these two triangles are congruent. find the size of the angle ∠def. lets try that again ∠def =

Explanation:

Step1: Recall congruent triangle property

Congruent triangles have corresponding angles equal. So, we need to find the corresponding angle to \( \angle DEF \) in \( \triangle ABC \).

Step2: Identify corresponding angles

In \( \triangle ABC \), the angles are \( \angle A = 84^\circ \), \( \angle B = 57^\circ \), \( \angle C = 39^\circ \). In \( \triangle DEF \), \( \angle D = 84^\circ \) (corresponding to \( \angle A \)). The side markings show the corresponding sides, so the angle corresponding to \( \angle C \) (which is \( 39^\circ \)) should be \( \angle DEF \) because of the congruence of triangles (corresponding angles in congruent triangles are equal). Thus, \( \angle DEF = 39^\circ \).

Answer:

39°