document.write( "Question 1189064: If a sphere has a radius of 6cm rests on 3 horizontal wires forming a plane triangle whose sides are 5cm, 12cm, and 13cm. Find the height of the top of the sphere above the plane of the wires.
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Algebra.Com's Answer #820283 by ikleyn(52943)\"\" \"About 
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\n" ); document.write( "If a sphere has a radius of 6cm rests on 3 horizontal wires forming a plane triangle
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document.write( "The plane of triangle cuts the sphere, and the section is the circle inscribed in the triangle.\r\n" );
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document.write( "For any triangle, the radius of the inscribed circle is the area of the triangle divided by its semi-perimeter\r\n" );
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document.write( "    r = \"S%2F%28%28P%2F2%29%29\".\r\n" );
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document.write( "In our case, the triangle is right-angled (the triple 5,12,13 is the Pythagorean triple), \r\n" );
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document.write( "so its area is half the product of its legs S = \"%281%2F2%29%2A5%2A12\" = 30 cm^2.\r\n" );
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document.write( "The perimeter of the triangle is  P = 5 + 12 + 13 = 30 cm.\r\n" );
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document.write( "So, the radius of the inscribed circle is r = \"30%2F%28%2830%2F2%29%29\" = 2 cm.\r\n" );
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document.write( "Hence, the distance from the center of the sphere to the cutting plane is  \"sqrt%286%5E2+-+2%5E2%29\" = \"sqrt%2836-4%29\" = \"sqrt%2832%29\" = \"4%2Asqrt%282%29\" cm.\r\n" );
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document.write( "The top of the sphere above the cutting plane is  6 + \"sqrt%2832%29\" = 11.657 cm (rounded).    ANSWER\r\n" );
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