document.write( "Question 557966: What is the length of the shortest altitude of a triangle with the sides of 13, 14, and 15? \n" ); document.write( "
Algebra.Com's Answer #362993 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "The other tutor's answer is correct, but maybe you're studying the \r\n" );
document.write( "law of cosines instead of Heron's formula.  And maybe you haven't\r\n" );
document.write( "proved that the shortest altitude is the one to the longest side.\r\n" );
document.write( "(His \"inverse proportional\" statement is incorrect).\r\n" );
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document.write( "Maybe this is the approach you should take.\r\n" );
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document.write( "Let's draw the three altitudes:\r\n" );
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document.write( "The law of cosines for the cos(A) is\r\n" );
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document.write( "\"cos%28A%29\" = \"%28b%5E2%2Bc%5E2-a%5E2%29%2F%282bc%29\" = \"%2813%5E2%2B14%5E2-15%5E2%29%2F%282%2A13%2A14%29\" = \"140%2F264\" = \"5%2F13\" \r\n" );
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document.write( "\"h%5B1%5D%2Fb\" = \"sin%28A%29\" = \"sqrt%281-cos%5E2%28A%29%29\" = \"sqrt%281-%285%2F13%29%5E2%29\" = \"sqrt%281-25%2F169%29\" = \"sqrt%28169%2F169-25%2F169%29\" = \"sqrt%28144%2F169%29\" = \"12%2F13\"\r\n" );
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document.write( "\"h%5B1%5D%2Fb\" = \"12%2F13\"\r\n" );
document.write( "\"h%5B1%5D%2F13\" = \"12%2F13\"\r\n" );
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document.write( "Multiply both sides by 13:\r\n" );
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document.write( "\"h%5B1%5D+=+12\"\r\n" );
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document.write( "The law of cosines for cos(B)\r\n" );
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document.write( "\"cos%28B%29\" = \"%28a%5E2%2Bc%5E2-b%5E2%29%2F%282ac%29\" = \"%2815%5E2%2B14%5E2-13%5E2%29%2F%282%2A15%2A14%29\" = \"252%2F420\" = \"3%2F5\"\r\n" );
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document.write( "\"h%5B2%5D%2Fc\" = \"sin%28B%29\" = \"sqrt%281-cos%5E2%28B%29%29\" = \"sqrt%281-%283%2F5%29%5E2%29\" = \"sqrt%281-9%2F25%29\" = \"sqrt%2825%2F25-9%2F25%29\" = \"sqrt%2816%2F25%29\" = \"4%2F5\"\r\n" );
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document.write( "\"h%5B2%5D%2Fc\" = \"4%2F5\"\r\n" );
document.write( "\"h%5B2%5D%2F14\" = \"4%2F5\"\r\n" );
document.write( "Cross multiply\r\n" );
document.write( "\"5h%5B2%5D+=+56\"\r\n" );
document.write( "\"h%5B2%5D+=56%2F5\"\r\n" );
document.write( "\"h%5B2%5D=11.2\"\r\n" );
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document.write( "\"h%5B3%5D%2Fc\" = \"sin%28A%29\" which we have already calculated as \"12%2F13\"\r\n" );
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document.write( "\"h%5B3%5D%2Fc\" = \"12%2F13\"\r\n" );
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document.write( "\"h%5B3%5D%2F14\" = \"12%2F13\"\r\n" );
document.write( "Cross multiply\r\n" );
document.write( "\"13h%5B3%5D+=+168\"\r\n" );
document.write( "\"h%5B3%5D+=168%2F13\"\r\n" );
document.write( "\"h%5B3%5D=12.92307692\"\r\n" );
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document.write( "So \"h%5B2%5D=11.2\" is the shortest altitude.\r\n" );
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document.write( "Incidentally, if you draw all three altitudes, they all three\r\n" );
document.write( "intersect at the same point, called the orthocenter.\r\n" );
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document.write( "Edwin
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