document.write( "Question 1112371: Given that tanα=8/15 (180°<α<270°). Find Cos(α/2) \n" ); document.write( "

Algebra.Com's Answer #727427 by mananth(16946) $\"\"$ $\"About$

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$\"alpha\"$ is in III quadrant\r
\n" ); document.write( "\n" ); document.write( "use Pythagoras theorem\r
\n" ); document.write( "\n" ); document.write( " $\"sqrt%288%5E2%2B15%5E2%29\"$ = hypotenuse =17\r
\n" ); document.write( "\n" ); document.write( "cos $\"alpha\"$ = 15/17\r
\n" ); document.write( "\n" ); document.write( " $\"2cos%5E2%28%28alpha%29%2F2%29\"$ = $\"1%2Bcos%28alpha%29\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"2cos%5E2%28%28alpha%29%2F2%29\"$ = $\"1%2B%2815%2F17%29\"$ \r
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\n" ); document.write( "\n" ); document.write( " $\"2cos%5E2%28%28alpha%29%2F2%29\"$ = $\"32%2F17%29\"$ \r
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\n" ); document.write( "\n" ); document.write( " $\"cos%5E2%28%28alpha%29%2F2%29\"$ = $\"16%2F17%29\"$ \r
\n" ); document.write( "\n" ); document.write( "cos $\"alpha\"$ = $\"4%2Fsqrt%2817%29\"$
\n" ); document.write( " $\"alpha\"$ is in III quadrant so ....\r
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