A square with a side of 9√2 is inscribed in a circle. Find the side of a regular triangle circumscribed about this circle.

Construct the diagonal MP of the square, which will be the diagonal of the square described around it.

The triangle KMP is rectangular, then, by the Pythagorean theorem, MP ^ 2 = 2 * KM ^ 2 = 2 * (9 * √2) ^ 2 = 324.

MP = 18 cm.

Then the radius of the circle is: R = MP / 2 = 18/2 = 9 cm.

The radius of a circle inscribed in an equilateral triangle is:

R = AB * √3 / 6, then AB = 6 * R / √3 = 6 * 9 / √3 = 54 / √3 = 18 * √3 cm.

Answer: The side of the triangle is 18 * √3 cm.



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