document.write( "Question 79822This question is from textbook Algebra 2 with Trigonometry
\n" ); document.write( ": cos2xcosx+sin2xsinx=1\r
\n" ); document.write( "\n" ); document.write( "I have to solve this problem in terms of the unit circle by using the Double Angle Identities, but I have no idea how to solve the problem after I plug them in. So far I have: (cos^2x-sin^2x)*(cosx)+(2sinx-cosx)*(sinx)=1 Is this even close to being on the right track? If someone could just help me get to what sinx and cosx equal I can find the radian angles from there. Thanks!!!\r
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Algebra.Com's Answer #57277 by Edwin McCravy(20060)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "cos(2x)cos(x) + sin(2x)sin(x) = 1\r\n" );
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document.write( "You are going about it wrong.  You were\r\n" );
document.write( "expected to recognize that the left side \r\n" );
document.write( "of that equation looks very much \r\n" );
document.write( "like the right side of the double\r\n" );
document.write( "angle identity:\r\n" );
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document.write( "cos(A-B) = cos(A)cos(B) + sin(A)sin(B)\r\n" );
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document.write( "where A = 2x and B = x\r\n" );
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document.write( "So the left side of your original equation\r\n" );
document.write( "can be replaced by cos(2x-x) from the left\r\n" );
document.write( "side of the identity.\r\n" );
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document.write( "and immediately you can write\r\n" );
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document.write( "  cos(2x-x) = 1\r\n" );
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document.write( "     cos(x) = 1\r\n" );
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document.write( "So the answer is \r\n" );
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document.write( "          x = 0 \r\n" );
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document.write( "Or, if your teacher wants all real solutions it is \r\n" );
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document.write( "          x = 2np for all integers n.\r\n" );
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document.write( "Edwin
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