The answer is below.
Work Step by Step
1. We are told XYZ is an isosceles triangle, so angle Y and Z are congruent by the definition of isosceles triangles. 2. Since YZ and XA are parallel, angle one is congruent to angle Y by the corresponding angles theorem, and angle Z is congruent to angle 2 by the alternate interior angles theorem. 3. From (1), we know that Y and Z are congruent, so the angles that are congruent to either Y or Z are congruent to each other. 4. Thus, angles one and two are congruent.