document.write( "Question 476923: Simplify the following:
\n" ); document.write( "sin (90° + x) sin (180° + x) + cos (90° + x) cos (180° – x) \n" ); document.write( "

Algebra.Com's Answer #327015 by robertb(5830) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"cos%2890%5Eo+%2B+x%29+=+-sinx\"$
\n" ); document.write( " $\"cos%28180%5Eo+-+x%29+=+-cosx\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"sin%28180%5Eo+%2B+x%29+=+-sinx\"$
\n" ); document.write( " $\"sin%2890%5Eo+%2B+x%29+=+cosx\"$ \r
\n" ); document.write( "\n" ); document.write( "==>sin (90° + x) sin (180° + x) + cos (90° + x) cos (180° – x) =
\n" ); document.write( "cosx*-sinx + -sinx*-cosx = -sinx*cosx + sinx*cosx = 0. \n" ); document.write( "

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