document.write( "Question 1088789: The exact value of $\"cos%28pi%2F7%29%2Bcos%5E2%28pi%2F7%29-2cos%5E3%28pi%2F7%29\"$ is a rational number in the form p/q, where p and q are integers. Find (p+q) \n" ); document.write( "

Algebra.Com's Answer #703165 by Edwin McCravy(20056) $\"\"$ $\"About$

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document.write( ", solving for cos²(x),\r\n" );
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document.write( "So we solve this for  cos³(x),\r\n" );
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document.write( "Solving for cos³(x)\r\n" );
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document.write( "So \r\n" );
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document.write( "(expression 1):   \r\n" );
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document.write( "Expression 1 is what we must evaluate.  \r\n" );
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document.write( "  \r\n" );
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document.write( "(equation 2)  \r\n" );
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document.write( "We set the real part of the left side of equation 2 \r\n" );
document.write( "equal to the real part of the right side of equation 2.\r\n" );
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document.write( "Now we use identities of angles subtracted from pi to reduce\r\n" );
document.write( "the angles:\r\n" );
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document.write( "Substituting\r\n" );
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document.write( "(equation 3):   \r\n" );
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document.write( "Now we go back to expression (1)\r\n" );
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document.write( "(expression 1):   \r\n" );
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document.write( "and use equation 3 to substitute 1/2 for the first three terms in \r\n" );
document.write( "the parentheses of expression (1):\r\n" );
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document.write( "So \r\n" );
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document.write( "and \r\n" );
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document.write( "Edwin

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