document.write( "Question 1161703: If tan²x = 1 + 2tan²y
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Algebra.Com's Answer #785452 by Edwin McCravy(20081)\"\" \"About 
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If tan²x = 1 + 2tan²y
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document.write( "tan²x = 1 + 2tan²y\r\n" );
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document.write( "Use the identity\r\n" );
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document.write( "          \"1%2Btan%5E2%28theta%29=sec%5E2%28theta%29\" \r\n" );
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document.write( "rewritten as \r\n" );
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document.write( "          \"tan%5E2%28theta%29=sec%5E2%28theta%29-1\"\r\n" );
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document.write( "\"sec%5E2%28x%29-1+=+1+%2B+2%28sec%5E2%28y%29-1%29\"\r\n" );
document.write( "\"sec%5E2%28x%29-1+=+1%2B2sec%5E2%28y%29-2\"\r\n" );
document.write( "\"sec%5E2%28x%29-1+=+2sec%5E2%28y%29-1\"\r\n" );
document.write( "\"sec%5E2%28x%29=2sec%5E2%28y%29\"\r\n" );
document.write( "\"1%2Fcos%5E2%28x%29=2%281%2Fcos%5E2%28y%29%29\"\r\n" );
document.write( "\"1%2Fcos%5E2%28x%29=2%2Fcos%5E2%28y%29\"\r\n" );
document.write( "\"cos%5E2%28y%29=2cos%5E2%28x%29\"\r\n" );
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document.write( "Use the identity\r\n" );
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document.write( "          \"sin%5E2%28theta%29%2Bcos%5E2%28theta%29=1\" \r\n" );
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document.write( "rewritten as \r\n" );
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document.write( "          \"cos%5E2%28theta%29=1-sin%5E2%28theta%29\"\r\n" );
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document.write( "on the left side\r\n" );
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document.write( "Use the identity \r\n" );
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document.write( "          \"cos%282theta%29=2cos%5E2%28theta%29-1\"\r\n" );
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document.write( "rewritten as\r\n" );
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document.write( "          \"2cos%5E2%28theta%29=cos%282theta%29%2B1\"\r\n" );
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document.write( "on the right side\r\n" );
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document.write( "\"1-sin%5E2%28y%29=cos%282x%29%2B1\"\r\n" );
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document.write( "Subtract 1 from both sides:\r\n" );
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document.write( "\"-sin%5E2%28y%29=cos%282x%29\"\r\n" );
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document.write( "add sin²(x) to both sides:\r\n" );
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document.write( "\"0=cos%282x%29%2Bsin%5E2%28x%29\"\r\n" );
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document.write( "Swap sides:\r\n" );
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document.write( "\"cos%282x%29%2Bsin%5E2%28x%29=0\" \r\n" );
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document.write( "Edwin
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