document.write( "Question 488238: sin 2x + cos 60 = 0, 0 < x < 360.
\n" ); document.write( "i have been able to find out that sin inverse of -1/2 is -30, but how do i find answers in the 3rd and fourth quadrant for 2x?? then i can find x. my answers are coming wrong, and i can apply no suitable rule. please help, and show working if possible.
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Algebra.Com's Answer #333323 by stanbon(75887)\"\" \"About 
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sin 2x + cos 60 = 0, 0 < x < 360.
\n" ); document.write( "i have been able to find out that sin inverse of -1/2 is -30, but how do i find answers in the 3rd and fourth quadrant for 2x?? then i can find x. my answers are coming wrong, and i can apply no suitable rule. please help, and show working if possible.\r
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\n" ); document.write( "sin(2x) + (1/2) = 0
\n" ); document.write( "sin(2x) = -1/2
\n" ); document.write( "2x = arcsin(-1/2) = 210 or 330
\n" ); document.write( "x = 105 or 165 degrees
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\n" ); document.write( "Note: If you know sin(theta) = 1/2
\n" ); document.write( "then sin(180-theta) = 1/2
\n" ); document.write( "and sin(180+theta) = -1/2
\n" ); document.write( "and sin(360-theta) = -1/2
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\n" ); document.write( "You can find those relationships
\n" ); document.write( "on the unit circle.\r
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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