document.write( "Question 1012725: Which sum or difference identity would you use to verify that cos(90 + theta) = -sin(theta)? \n" ); document.write( "

Algebra.Com's Answer #628760 by fractalier(6550) $\"\"$ $\"About$

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cos(a + b) = cos a * cos b - sin a * sin b \n" ); document.write( "

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