document.write( "Question 1029655: Evaluate: 2cos^2(7pi/12) - 1 \n" ); document.write( "

Algebra.Com's Answer #644618 by fractalier(6550) $\"\"$ $\"About$

You can put this solution on YOUR website!
For this one we can use the identity:
\n" ); document.write( " $\"cos%282%2A%28theta%29%29+=+2%2A%28cos%28theta%29%29%5E2+-+1\"$
\n" ); document.write( "but we'll go backwards...thus
\n" ); document.write( "2cos^2(7pi/12) - 1 = cos(2*(7pi/12)) = cos(7pi/6) = -cos(pi/6) =
\n" ); document.write( " $\"-sqrt%283%29+%2F+2\"$ \n" ); document.write( "

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