document.write( "Question 478143: how do you find the largest angle of a triangle with sides 4cm, 7cm and 9cm? \n" ); document.write( "
Algebra.Com's Answer #852395 by ikleyn(52969)\"\" \"About 
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\n" ); document.write( "How do you find the largest angle of a triangle with sides 4cm, 7cm and 9cm?
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document.write( "The largest angle is opposite to the longest side, which is 9 cm.\r\n" );
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document.write( "To find its measure  \"alpha\",  use the cosine law\r\n" );
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document.write( "    \"9%5E2\" = \"4%5E2+%2B+7%5E2+-+2%2A4%2A7%2Acos%28alpha%29\",\r\n" );
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document.write( "    cos(alpha) = \"%284%5E2%2B7%5E2-9%5E2%29%2F%282%2A4%2A7%29\" = -0.285714286.    \r\n" );
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document.write( "    \"alpha\" = arccos(-0.285714286) = 106.60 degrees  (approximately).    <<<---===  ANSWER\r\n" );
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