document.write( "Question 1040635: If cosA = 8/17 and cosecB = 5/4 and both A and B are acute angles. Calculate the value of cos(A-B) without using a calculator. \n" ); document.write( "

Algebra.Com's Answer #655519 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"cos%28A%29=8%2F17\"$
\n" ); document.write( " $\"sin%28B%29=4%2F5\"$
\n" ); document.write( "Use
\n" ); document.write( " $\"cos%5E2%28C%29%2Bsin%5E2%28C%29=1\"$
\n" ); document.write( "to find $\"sin%28A%29\"$ and $\"cos%28B%29\"$ .
\n" ); document.write( " $\"%288%2F17%29%5E2%2Bsin%5E2%28A%29=1\"$
\n" ); document.write( " $\"64%2F289%2Bsin%5E2%28A%29=1\"$
\n" ); document.write( " $\"sin%5E2%28A%29=%28289-64%29%2F289\"$
\n" ); document.write( " $\"sin%5E2%28A%29=225%2F289\"$
\n" ); document.write( " $\"sin%28A%29=15%2F17\"$
\n" ); document.write( "and
\n" ); document.write( " $\"cos%28B%29%5E2%2B%284%2F5%29%5E2=1\"$
\n" ); document.write( " $\"cos%28B%29%5E2%2B16%2F25=1\"$
\n" ); document.write( " $\"cos%28B%29%5E2=9%2F25\"$
\n" ); document.write( " $\"cos%28B%29=3%2F5\"$
\n" ); document.write( "Then use the formula,
\n" ); document.write( " $\"cos%28A-B%29=cos%28A%29cos%28B%29%2Bsin%28A%29sin%28B%29\"$
\n" ); document.write( "Substitute,
\n" ); document.write( " $\"cos%28A-B%29=%288%2F17%29%283%2F5%29%2B%2815%2F17%29%284%2F5%29\"$
\n" ); document.write( "Complete that for the final answer.\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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