The circumference of the described quadrilateral ABCD is 36 cm. Find side AB if it is three times the size of side CD.

Since a circle is inscribed in the quadrilateral ABCD, the sums of the lengths of its opposite sides are equal.

AB + CD = AD + BC.

Ravsd = (AB + CD) + (AD + BC) = 2 * (AB + CD) = 36 cm.

AB + CD = 36/2 = 18 cm.

By condition, AB = 3 * CD.

3 * CD + CD = 18.

CD = 18/4 = 4.5 cm.

AB = 3 * 4.5 = 13.5 cm.

Answer: The length of the AB side is 13.5 cm.



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