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4. Find the radius of the inscribed circle in quadrilateral ABCD if the area of ABCD is 240 cm2 and its perimeter is 64 cm. 5. Find the area of a quadrilateral is its diagonals are 5 cm and 8 cm, and the angle between them is 450 . 6. Find the angle measure of a regular polygon with 20 sides. 7. Find the number of sides of a regular polygon with angle measure 1650. 8. Find the central angle of the circumscribed circle around a polygon with 10 sides. 9. Find the radii of the inscribed and circumscribed circles for a regular 12-gon with a side 20 cm. 10. Find the side and the area of a regular hexagon if the radius of its inscribed circle is 8 cm