document.write( "Question 1011265: If sin A sin B = cos A cos B , then cos(A - B ) = ? \n" ); document.write( "

Algebra.Com's Answer #626881 by MathLover1(20850) $\"\"$ $\"About$

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by definition, $\"cos%28A-B%29+=+cos+%28A%29+cos+%28B%29+%2B+sin%28+A%29+sin%28+B%29\"$ \r
\n" ); document.write( "\n" ); document.write( "so, if $\"sin%28A%29+sin+%28B%29+=+cos+%28A%29+cos+%28B%29\"$ , then\r
\n" ); document.write( "\n" ); document.write( " $\"cos%28A-B%29+=+cos%28+A%29+cos+%28B%29+%2B+cos+%28A%29+cos+%28B%29\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"cos%28A-B%29+=2+cos%28+A+%29cos+%28B+%29\"$ \n" ); document.write( "

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