After a 10 meter long rope goes around a tree trunk for three times, the remaining 0.58 meters. What is the cross-sectional area of the tree trunk?

(10-0.58) △ 3 = 9.42 △ 3 = 3.14 (m) 3.14 △ 3.14 △ 2 = 0.5 (m), 3.14 × 0.52 = 0.785 (M2); a: the cross-sectional area of trunk is 0.785 m2

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