document.write( "Question 918988: Find sin2x, cos2x, and tan2x under the given conditions
\n" ); document.write( "cosx=-3/5, for 3pie/2 < x < 2pie
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Algebra.Com's Answer #557383 by lwsshak3(11628)\"\" \"About 
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Find sin2x, cos2x, and tan2x under the given conditions
\n" ); document.write( "cosx=-3/5, for pie < x < 3pie/2
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\n" ); document.write( "You are working with a 3-4-5 reference right triangle in quadrant III where cos<0, sin<0
\n" ); document.write( "cosx=-3/5
\n" ); document.write( "sinx=-4/5
\n" ); document.write( "..
\n" ); document.write( "sin2x=2sinxcosx=2*-4/5*-3/5=24/25
\n" ); document.write( "cos2x=cos^2x-sin^2x=(-3/5)^2-(4/5)^2=9/25-16/25=-7/25
\n" ); document.write( "tan2x=sin2x/cos2x=-24/7
\n" ); document.write( "..
\n" ); document.write( "Check:
\n" ); document.write( "cosx=-3/5(in quadrant III)
\n" ); document.write( "x=233.13˚
\n" ); document.write( "2x=466.26˚
\n" ); document.write( "..
\n" ); document.write( "sin2x=sin(466.26˚)≈0.9600...
\n" ); document.write( "exact value=24/25=0.9600
\n" ); document.write( "..
\n" ); document.write( "cos2x=cos(466.26˚)≈-0.2799...
\n" ); document.write( "exact value=-7/25=-0.2800
\n" ); document.write( "..
\n" ); document.write( "tan2x=tan(466.26˚)≈-3.4286...
\n" ); document.write( "exact value=-24/7≈-3.4285... \n" ); document.write( "
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