document.write( "Question 969905: How do I find sin and cos of theta if tangent of theta equals -1?
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Algebra.Com's Answer #592628 by AnlytcPhil(1806) $\"\"$ $\"About$

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How do I find sin and cos of theta if tangent of theta equals -1?
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document.write( "The tangent is negative in the 2nd and 4th quadrants.  Its referent angle\r\n" );
document.write( "is the first quadrant angle that has +1 for its tangent.  That's  or .  \r\n" );
document.write( "Its sine is  and its cosine is also \r\n" );
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document.write( "So to get the smallest 2nd quadrant positive solution, we either\r\n" );
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document.write( "subtract 45° from 180° to get it into the 2nd quadrant, and get \r\n" );
document.write( "180°-45° = 135°.  Its sine is  and it's cosine is .\r\n" );
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document.write( "or we\r\n" );
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document.write( "subtract  from  to get it into the 2nd quadrant, \r\n" );
document.write( "and get \r\n" );
document.write( ", and its sine is  and its cosine is \r\n" );
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document.write( "That's the 2nd quadrant solutions worked out in both degrees and radians.\r\n" );
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document.write( "To get the smallest 4th quadrant positive solution, we either\r\n" );
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document.write( "subtract 45° from 360° to get it into the 4th quadrant, and get \r\n" );
document.write( "360°-45° = 315°,\r\n" );
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document.write( "or we\r\n" );
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document.write( "subtract  from  to get it into the 4th quadrant, \r\n" );
document.write( "and get \r\n" );
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document.write( ".\r\n" );
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document.write( "The sine is , and the cosine is \r\n" );
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document.write( "That's the 4th quadrant solutions worked out in both degrees and radians.  \r\n" );
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document.write( "So if theta is in the 2nd quadrant its sine is  and its \r\n" );
document.write( "cosine is , and\r\n" );
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document.write( "if theta is in the 4th quadrant its sine is  and its cosine \r\n" );
document.write( "is .\r\n" );
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document.write( "Edwin

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