document.write( "Question 964658: cos5xcos2x+sin5xsin2x= -1 for x is greater or equal to 0, and less than or equal to 2pi \n" ); document.write( "

Algebra.Com's Answer #589531 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
Use the identity,
\n" ); document.write( " $\"cos%28x-y%29=cos%28x%29cos%28y%29%2Bsin%28x%29sin%28y%29\"$
\n" ); document.write( ".
\n" ); document.write( ".
\n" ); document.write( " $\"cos%285x-2x%29=-1\"$
\n" ); document.write( " $\"cos%283x%29=-1\"$
\n" ); document.write( " $\"3x%2B2pi%2Ak=pi\"$
\n" ); document.write( " $\"x=pi%2F3%2B%282%2F3%29pi%2Ak\"$
\n" ); document.write( " $\"x=%281%2F3%29pi\"$ <-- $\"k=0\"$
\n" ); document.write( " $\"x=%283%2F3%29pi=pi\"$ <-- $\"k=1\"$
\n" ); document.write( " $\"x=%285%2F3%29pi\"$ <-- $\"k=2\"$ \n" ); document.write( "

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