\r\n" );
document.write( "We draw the triangle to see what it looks like:\r\n" );
document.write( "\r\n" );
document.write( " (3, -2), (7, 3), and (-7, 6) \r\n" );
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document.write( "
\r\n" );
document.write( "\r\n" );
document.write( "Looks suspiciously like the angle down at (3,-2) is a right\r\n" );
document.write( "angle. So let's see if we can prove that it is.\r\n" );
document.write( "\r\n" );
document.write( "We find the slopes of its two sides and if that's a right angle \r\n" );
document.write( "then the slope of one with be the reciprocal of the other with\r\n" );
document.write( "the opposite sign\r\n" );
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document.write( "We use the slope formula:\r\n" );
document.write( "\r\n" );
document.write( "
\r\n" );
document.write( "where (x1,y1) = (-7,6)\r\n" );
document.write( "and where (x2,y2) = (3,-2)\r\n" );
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document.write( "
\r\n" );
document.write( "
\r\n" );
document.write( "\r\n" );
document.write( "We use the slope formula again:\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "this time with (x1,y1) = (7,3)\r\n" );
document.write( "and where (x2,y2) = (3,-2)\r\n" );
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document.write( "
\r\n" );
document.write( "
\r\n" );
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document.write( "Indeed and are reciprocals with\r\n" );
document.write( "opposite signs, so the sides are perpendicular and\r\n" );
document.write( "the angle with vertex (3,-2) is a right angle.\r\n" );
document.write( "\r\n" );
document.write( "So the triangle is a right triangle.\r\n" );
document.write( "\r\n" );
document.write( "Edwin
\n" );
document.write( "![\"\"](\"/images/stars/stars-13.gif\")
