A circle is inscribed in the trapezoid, the sum of the lengths of the sides of which is 30. Find the length of the midline of the trapezoid

According to the second property of the quadrangle: AB + CD = BC + AD = 30
By definition of the midline of the trapezoid: m = (BC + AD) / 2 = 30/2 = 15
Answer: m = 15

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