document.write( "Question 873813: How do I solve this? Use the exact values of the sine and cosine of 2π/3 and π /4, and the angle sum identity for sine, to find the exact value of sin(11 π /12). \n" ); document.write( "
Algebra.Com's Answer #527140 by KMST(5328)\"\" \"About 
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The angle sum identity for sine is
\n" ); document.write( "\"sin%28A%2BB%29=sin%28A%29%2Acos%28B%29%2Bcos%28A%29%2Asin%28B%29\"
\n" ); document.write( "Since \"2pi%2F3%2Bpi%2F4=8pi%2F12%2B3pi%2F12=11pi%2F12\" ,
\n" ); document.write( "you can use the angle sum identity (above),
\n" ); document.write( "and the values for sine and cosine of \"2pi%2F3\" and \"pi%2F4\"
\n" ); document.write( "to find \"sin%2811pi%2F12%29=sin%282pi%2F3%2Bpi%2F4%29\" .
\n" ); document.write( "\"sin%28pi%2F4%29\" and \"cos%28pi%2F4%29\" are easy. \"pi%2F4\" is \"45%5Eo\" ,
\n" ); document.write( "and \"sin%28pi%2F4%29=cos%28pi%2F4%29=sqrt%282%29%2F2\" .
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\n" ); document.write( "\"2pi%2F3\" is a little harder because it is in quadrant II.
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\n" ); document.write( "\n" ); document.write( "\"sin%282pi%2F3%29=sin%28pi-2pi%2F3%29=sin%28pi%2F3%29=sqrt%283%29%2F2\"
\n" ); document.write( "\"cos%282pi%2F3%29=-cos%28pi-2pi%2F3%29=-cos%28pi%2F3%29=-1%2F2\"
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\n" ); document.write( "So, applying \"sin%28A%2BB%29=sin%28A%29%2Acos%28B%29%2Bcos%28A%29%2Asin%28B%29\" with \"A=2pi%2F3\" and \"B=pi%2F4\"
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\n" ); document.write( "That could be \"simplified\" different ways:
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\n" ); document.write( "or
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\n" ); document.write( "Those expressions are the exact value of \"sin%2811pi%2F12%29\"
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