document.write( "Question 932139: use double angle identity to find exact value of 2cos^2(75 degrees)-1 \n" ); document.write( "

Algebra.Com's Answer #566037 by lwsshak3(11628) $\"\"$ $\"About$

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use double angle identity to find exact value of 2cos^2(75 degrees)-1
\n" ); document.write( "2(cos^2(75))-1
\n" ); document.write( "2(1-sin^2(75)-1
\n" ); document.write( "2-2sin^2(75)-1
\n" ); document.write( "1-2sin^2(75)=cos(150)=-√3/2 (In quadrant II where cos<0) \n" ); document.write( "

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