Final answer:
Macy can construct only one isosceles triangle using this information.
Step-by-step explanation:
An isosceles triangle has two equal angles and two equal sides.
If the unique angle of the triangle is 40°, the other two angles must be equal to each other. Since the sum of angles in a triangle is always 180°, the sum of the two equal angles is 180° - 40° = 140°.
Since the two equal angles are congruent, their measure is each 140° ÷ 2 = 70°.
The base of the triangle is opposite the unique angle. Since the length of the base is 6 centimeters, the length of each congruent side is also 6 centimeters.
Therefore, Macy can construct only one isosceles triangle using this information.