document.write( "Question 289398: Find $\"+sin2x+\"$ if $\"+secx=-4+\"$ and $\"+sinx%3C0+\"$ \n" ); document.write( "

Algebra.Com's Answer #209617 by Edwin McCravy(20065) $\"\"$ $\"About$

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Find $\"+sin2x+\"$ if $\"+secx=-4+\"$ and $\"+sinx%3C0+\"$ \r
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document.write( "Since the secant and the sine of x are both negative, that means\r\n" );
document.write( "x is in the third quadrant. between 180° and 270° in degress,\r\n" );
document.write( "or between  and  in radians.  So therefore\r\n" );
document.write( "2x will be between 360° and 540° which is actually the 1st and\r\n" );
document.write( "2nd quadrants.  The sine is positive in both the 1st and 2nd\r\n" );
document.write( "quadrants, so the answer will be posotive.\r\n" );
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document.write( "We need these identities:\r\n" );
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document.write( "1. \r\n" );
document.write( "2.  \r\n" );
document.write( "3.  \r\n" );
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document.write( "First we'll find  using 3.\r\n" );
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document.write( "Next we'll find  using 2.\r\n" );
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document.write( "However, since  we take the negative sign,\r\n" );
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document.write( "Now we can substitute in 1:\r\n" );
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document.write( "Edwin

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