Final answer:
Angle C in triangle ABC measures 70.5 degrees.
Step-by-step explanation:
Given triangle ABC with AB congruent to AC and angle B measuring 39 degrees, we can use the fact that the sum of the angles in a triangle is 180 degrees to find the measure of angle C. Since AB is congruent to AC, we know that angles A and C are congruent. Let x represent the measure of angle C, so angle A also measures x degrees. The sum of the angles in triangle ABC is 39 + x + x = 180. Simplifying the equation, we find 39 + 2x = 180. Subtracting 39 from both sides gives 2x = 141. Finally, dividing both sides by 2 gives x = 70.5 degrees. Therefore, angle C measures 70.5 degrees.