document.write( "Question 1157854: Find all points on the circle x^2 + y^2 = 81 where the slope is 9/40.\r
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Algebra.Com's Answer #780747 by Edwin McCravy(20054) $\"\"$ $\"About$

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document.write( "That means:\r\n" );
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document.write( "Find all points on the circle x^2 + y^2 = 81 where the slope OF A LINE DRAWN\r\n" );
document.write( "TANGENT TO THE CIRCLE AT THAT POINT is 9/40.\r\n" );
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document.write( "We take the derivative implicitly\r\n" );
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document.write( "Divide every term by 2\r\n" );
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document.write( "Substitute 9/40 for (dy)/(dx)\r\n" );
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document.write( "Solve for y:\r\n" );
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document.write( "Multiply both sides by 40/9\r\n" );
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document.write( "Substitute for y in the equation of the circle:\r\n" );
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document.write( "Multiply through by 81\r\n" );
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document.write( "Substituting for x² in the equation of the circle:\r\n" );
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document.write( "Multiply through by 1681\r\n" );
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document.write( "So the two points where the slope of the tangent line is 9/40 are:\r\n" );
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document.write( "and\r\n" );
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document.write( "Edwin

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