document.write( "Question 810472: Use the given information to find cos(x/2), sin(x/2), and tan(x/2): \r
\n" ); document.write( "\n" ); document.write( "Cos (x)=-4/5\r
\n" ); document.write( "\n" ); document.write( "180 degrees< x < 270 degrees \n" ); document.write( "
Algebra.Com's Answer #488556 by lwsshak3(11628)\"\" \"About 
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Use the given information to find exact answers for cos(x/2), sin(x/2), and tan(x/2):
\n" ); document.write( "Cos (x)=-4/5
\n" ); document.write( "180 degrees< x < 270 degrees
\n" ); document.write( "***
\n" ); document.write( "you are working with a 3-4-5 reference right triangle in quadrant III where sin>0, cos<0, tan>0.
\n" ); document.write( "..
\n" ); document.write( "cos(x)=-4/5 (given)
\n" ); document.write( "sin(x)=-3/5
\n" ); document.write( "tan(x)=sin/cos=3/5
\n" ); document.write( "..
\n" ); document.write( "\"cos%28x%2F2%29=-sqrt%28%281%2Bcos%28x%29%29%2F2%29%29\"
\n" ); document.write( "\"cos%28x%2F2%29=-sqrt%28%281-4%2F5%29%2F2%29=-sqrt%28%281%2F5%29%2F2%29=-sqrt%281%2F10%29\"
\n" ); document.write( "..
\n" ); document.write( "\"sin%28x%2F2%29=sqrt%28%281-cos%28x%29%29%2F2%29%29\"
\n" ); document.write( "\"sin%28x%2F2%29=sqrt%28%281%2B4%2F5%29%2F2%29=sqrt%28%289%2F5%29%2F2%29=sqrt%289%2F10%29\"
\n" ); document.write( "..
\n" ); document.write( "\"tan%28x%2F2%29=sin%28x%29%2F%281%2Bcos%28x%29%29\"
\n" ); document.write( "\"tan%28x%2F2%29=%28-3%2F5%29%2F%281-4%2F5%29=%28-3%2F5%29%2F%281%2F5%29=-3\"
\n" ); document.write( "..
\n" ); document.write( "Check:(w/calculator)
\n" ); document.write( "cos(x)=-4/5(in quadrant III)
\n" ); document.write( "x≈216.87˚
\n" ); document.write( "x/2≈108.43˚
\n" ); document.write( "..
\n" ); document.write( "cos(x/2)=cos(108.43˚)≈-0.316
\n" ); document.write( "exact value=-√(1/10)≈-0.316
\n" ); document.write( "..
\n" ); document.write( "sin(x/2)=sin(108.43˚)≈0.9487
\n" ); document.write( "exact value=√(9/10)≈0.9487
\n" ); document.write( "..
\n" ); document.write( "tan(x/2)=tan(108.43˚)≈-3.0000
\n" ); document.write( "exact value=-3.0000 \n" ); document.write( "
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