document.write( "Question 816468: If the cos x is -(1/2) and the x is in the 2nd quadrant, find the cos 2x. (no calculator)\r
\n" ); document.write( "\n" ); document.write( "I have been working on this problem for 30 mins. I think I am missing one thing for it to make sense. I think that sin x= 2/sq.rt. 5...\r
\n" ); document.write( "\n" ); document.write( "Show that this is a trig identity.
\n" ); document.write( "csc^2 = cot^2x+1 \n" ); document.write( "
Algebra.Com's Answer #491555 by lwsshak3(11628)\"\" \"About 
You can put this solution on YOUR website!
If the cos x is -(1/2) and the x is in the 2nd quadrant, find the cos 2x.
\n" ); document.write( "cos(2x)=cos^2(x)-sin^2(x)
\n" ); document.write( "..
\n" ); document.write( "cos(x)=(-1/2)
\n" ); document.write( "cos^2(x)=1/4
\n" ); document.write( "..
\n" ); document.write( "sin(x)=√3/2
\n" ); document.write( "sin^2(x)=3/4
\n" ); document.write( "..
\n" ); document.write( "cos(2x)=(1/4)-(12/16)=(4/16)-(12/16)=-8/16=-1/2
\n" ); document.write( "...
\n" ); document.write( "Show that this is a trig identity.
\n" ); document.write( "csc^2x = cot^2x+1
\n" ); document.write( "start with right side:
\n" ); document.write( "cot^2x+1=cos^2/sin^2x+1
\n" ); document.write( "(sin^2(x)+cos^2(x))/sin^2(x)
\n" ); document.write( "1/sin^2(x)=csc^2(x)
\n" ); document.write( "verified:
\n" ); document.write( "right side=left side
\n" ); document.write( " \n" ); document.write( "
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