document.write( "Question 313335: if tan A = 4/3 and tan B=12/5.find cos (A-B)
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Algebra.Com's Answer #224079 by Fombitz(32388) $\"\"$ $\"About$

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$\"tan%28A%29=sin%28A%29%2Fcos%28A%29\"$
\n" ); document.write( " $\"sin%28A%29=4%2FR\"$
\n" ); document.write( " $\"cos%28A%29=3%2FR\"$
\n" ); document.write( " $\"sin%5E2%28A%29%2Bcos%5E2%28A%29=1\"$
\n" ); document.write( " $\"16%2FR%5E2%2B9%2FR%5E2=1\"$
\n" ); document.write( " $\"25%2FR%5E2=1\"$
\n" ); document.write( " $\"R%5E2=25\"$
\n" ); document.write( " $\"R=5\"$
\n" ); document.write( " $\"sin%28A%29=4%2F5\"$
\n" ); document.write( " $\"cos%28A%29=3%2F5\"$
\n" ); document.write( "Similarly for $\"B\"$ ,
\n" ); document.write( " $\"144%2FR%5E2%2B25%2FR%5E2=1\"$
\n" ); document.write( " $\"169%2FR%5E2=1\"$
\n" ); document.write( " $\"R=13\"$
\n" ); document.write( " $\"sin%28B%29=12%2F13\"$
\n" ); document.write( " $\"cos%28B%29=5%2F13\"$
\n" ); document.write( "Use the trig identity,
\n" ); document.write( " $\"cos%28A-B%29=cos%28A%29cos%28B%29%2Bsin%28A%29sin%28B%29\"$
\n" ); document.write( " $\"cos%28A-B%29=%283%2F5%29%285%2F13%29%2B%284%2F5%29%2812%2F13%29+\"$
\n" ); document.write( " $\"cos%28A-B%29=%2815%2F65%29%2B%2848%2F65%29+\"$
\n" ); document.write( " $\"cos%28A-B%29=63%2F65\"$
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