You can
put this solution on YOUR website!simplify: sin(90degrees+ x) sin ( 180 degrees +x) + cos ( 90 degrees + x) cos ( 180 degrees - x ).
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There are several ways to work this problem; you might want to do it anothe way,
but here goes:
sin(90+x) = cosx
sin(180+x) = -sinx
cos(90+x) = -sinx
cos(180-x) = -cosx
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Your Problem:
cosx*(-sinx)+(-sinx)(-cosx)
==0
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Cheers,
Stan H.
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