Since a circle is inscribed in a circle, by its property, the sum of the lengths of the lateral sides of the trapezoid is equal to the sum of the lengths of its bases.
Since the trapezoid is isosceles, the sum of the lengths of the sides is 5 + 5 = 10 cm.
The empty smaller base is equal to X cm, then X + 8 = 10.
X = 10 – 8 = 2 cm.
Answer: The upper base of the trapezoid is 2 cm.
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