document.write( "Question 1019495: Two side of a parallelogram are 694 feet and 418 feet
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Algebra.Com's Answer #635459 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "We will be using the law of cosines.\r\n" );
document.write( "Since the adjacent interior angles of a parallogram are\r\n" );
document.write( "supplementary, cos(∠ABC) = -cos(∠DAB), so\r\n" );
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document.write( "Using the law of cosines on ΔABD\r\n" );
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document.write( "       BD² =  AD² +  AB² - 2∙ AD∙ AB∙cos(∠DAB)\r\n" );
document.write( "(1)   602² = 418² + 694² - 2∙418∙694∙cos(∠DAB)  \r\n" );
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document.write( "Using the law of cosines on ΔABC\r\n" );
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document.write( "       AC² =  BC² +  AB² - 2∙ BC ∙AB∙cos(∠ABC)\r\n" );
document.write( "       AC² = 418² + 694² - 2∙418∙694∙[-cos(∠DAB)]\r\n" );
document.write( "(2)    AC² = 418² + 694² + 2∙418∙694∙cos(∠DAB)\r\n" );
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document.write( "Adding equations (1) and (2)\r\n" );
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document.write( "(1)   602² = 418² + 694² - 2∙418∙694∙cos(∠DAB)\r\n" );
document.write( "(2)    AC² = 418² + 694² + 2∙418∙694∙cos(∠DAB)\r\n" );
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document.write( "602² + AC² = 2∙418² + 2∙694² \r\n" );
document.write( "       AC² = 2∙418² + 2∙694² - 602²\r\n" );
document.write( "       AC² = 2∙418² + 2∙694² - 602²\r\n" );
document.write( "       AC² = 349448 + 963272 - 362484\r\n" );
document.write( "       AC² = 950316\r\n" );
document.write( "        AC = √950316\r\n" );
document.write( "        AC = 974.8415256 ft.   \r\n" );
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document.write( "Edwin
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