document.write( "Question 799273: sin4x-2sin2x-1=0 \n" ); document.write( "
Algebra.Com's Answer #482677 by lwsshak3(11628)\"\" \"About 
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solve for x
\n" ); document.write( "sin^4x-2sin^2x-1=0
\n" ); document.write( "let u=sin^2x
\n" ); document.write( "u^2=sin^4x
\n" ); document.write( "u^2-2u-1=0
\n" ); document.write( "solve for u with quadratic formula:
\n" ); document.write( "\"u+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "a=1. b=-2, c=-1
\n" ); document.write( "ans:
\n" ); document.write( "u≈-0.4142(reject)
\n" ); document.write( "or
\n" ); document.write( "u≈2.4142
\n" ); document.write( "..
\n" ); document.write( "sin^2x=2.4142
\n" ); document.write( "x=±√2.4142≈±1.5537(radians) \n" ); document.write( "
\n" );