document.write( "Question 675749: Find the sin(x) if cos(2x)=2/3, with x terminating in quadrant III \n" ); document.write( "

Algebra.Com's Answer #420044 by MathLover1(20850) $\"\"$ $\"About$

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replace $\"cos%282x%29\"$ with $\"1-2%2Asin%5E2%28x%29\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"1-2sin%5E2%28x%29=2%2F3\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"-2sin%5E2%28x%29=2%2F3-1\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"-2sin%5E2%28x%29=-1%2F3\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"2sin%5E2%28x%29=1%2F3\"$
\n" ); document.write( "
\n" ); document.write( " $\"sin%5E2%28x%29=1%2F6\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"sin%28x%29=+sqrt%281%2F6%29\"$ \r
\n" ); document.write( "\n" ); document.write( "since $\"sin%28x%29\"$ is negative in quad III, solution is $\"sin%28x%29=+-sqrt%281%2F6%29=-0.408\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"x=-24.08\"$ degrees\r
\n" ); document.write( "\n" ); document.write( "or
\n" ); document.write( " $\"x=180-%28-24.08%29=180%2B24.08=204.08\"$ degrees.....in quadrant III
\n" ); document.write( " \n" ); document.write( "

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