document.write( "Question 451184: How do I develop the identity for $\"sin%28expr%281%2F2%29a%29\"$ by using the identity for $\"cos+%282a%29\"$ ? \n" ); document.write( "

Algebra.Com's Answer #310294 by Edwin McCravy(20081) $\"\"$ $\"About$

You can put this solution on YOUR website!

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document.write( "Start with the identity:\r\n" );
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document.write( " <-- sometimes this is given. If so you can start here\r\n" );
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document.write( "Now substitute \r\n" );
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document.write( "Do one cancellation on the right:\r\n" );
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document.write( "The sign to use depends on the quadrant\r\n" );
document.write( "in which the terminal side of  lies. \r\n" );
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document.write( "If the terminal side of  lies in the \r\n" );
document.write( "first or second quadrants, the identity uses the \r\n" );
document.write( "positive sign.\r\n" );
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document.write( "If the terminal side of  lies in the \r\n" );
document.write( "third or fourth quadrants, the identity uses the \r\n" );
document.write( "negative sign.\r\n" );
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document.write( "Edwin

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