document.write( "Question 759972: Find the exact values by applying the odd/even identities, cofunction identities, and cosine of sum or difference identities. Do not use a calculator.
\n" ); document.write( "sin(85°)sin(40°)+sine(-5°)sin(-50°) \n" ); document.write( "
Algebra.Com's Answer #462371 by lwsshak3(11628)\"\" \"About 
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Find the exact values by applying the odd/even identities, cofunction identities, and cosine of sum or difference identities. Do not use a calculator.
\n" ); document.write( "sin(85°)sin(40°)+sine(-5°)sin(-50°)
\n" ); document.write( "***
\n" ); document.write( "sin85º=cos(90-85)=cos5º
\n" ); document.write( "sin40º=cos(90-40)=cos50º
\n" ); document.write( "sin(-5º)=-sin5º
\n" ); document.write( "sin(-50º)=-sin50º
\n" ); document.write( "Identity: cos(s-t)=cos s cos t+sin s sin t
\n" ); document.write( "cos(50-5)=cos50º*cos5º+(-sin50º)*(-sin5º)
\n" ); document.write( "cos(50-5)=cos45º=√2/2
\n" ); document.write( "..
\n" ); document.write( "calculator check:
\n" ); document.write( "cos50º*cos5º+(-sin50º)*(-sin5º)≈0.6403+0.0667≈0.7071
\n" ); document.write( "Exact value=√2/2≈0.7071 \n" ); document.write( "
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