document.write( "Question 1079028: Prove that the sum of all three reflex exterior angle is always 900°. \n" ); document.write( "
Algebra.Com's Answer #693405 by Edwin McCravy(20062)\"\" \"About 
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document.write( "The reflex exterior angles are the outside angles indicated by \r\n" );
document.write( "the red arcs in this picture:\r\n" );
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document.write( "A reflex angle is 360° minus the acute or obtuse angle with\r\n" );
document.write( "the same sides.\r\n" );
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document.write( "Let the interior angles of a triangle be A, B, and C.\r\n" );
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document.write( "The sum of the interior angles of any triangle is 180°,\r\n" );
document.write( "So A+B+C = 180°\r\n" );
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document.write( "Then the reflex exterior angle at vertex A is 360°-A.\r\n" );
document.write( "Then the reflex exterior angle at vertex B is 360°-B.\r\n" );
document.write( "Then the reflex exterior angle at vertex C is 360°-C.\r\n" );
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document.write( "The sum of the reflex exterior angles is \r\n" );
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document.write( "(360°-A)+(360°-B)+(360°-C) = 360°-A+360°-B+360°-C\r\n" );
document.write( "1080°-A-B-C = 1080°-(A+B+C) = 1080°-180° = 900°\r\n" );
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document.write( "Edwin
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