document.write( "Question 1151636: Consider the following trigonometric equation:
\n" ); document.write( "\"2sin%28x%29cos%28x%29-3sin%28x%29-3cos%28x%29%2B3=0\"
\n" ); document.write( "A) It has the same solutions as the equation \"0=%28sin%28x%29%2Bcos%28x%29%29%5E2-3%28sin%28x%29%2Bcos%28x%29%29%2B2\"
\n" ); document.write( "B) the equation has no real solutions
\n" ); document.write( "C) It has the same solutions as the equation \"0=%28sqrt%282%29sin%28x%2Bpi%2F4%29-2%29%28sqrt%282%29sin%28x%2Bpi%2F4%29-1%29\"
\n" ); document.write( "D) It has the same solutions as the equation \"0=%28sqrt%282%29sin%28x%2Bpi%2F4%29%29%5E2-3%28sqrt%282%29sin%28x%2Bpi%2F4%29%29%2B2\"
\n" ); document.write( "E) none of these
\n" ); document.write( "Note: can you please show me how to find out whether the equation has a real solution or not.
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Algebra.Com's Answer #773493 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "\"%28A%2BB%29%5E2+=+A%5E2+%2B+2%2AA%2AB+%2B+B%5E2\"\r
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\n" ); document.write( "\n" ); document.write( " Plug in A = sin(x) and B = cos(x)\r
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\n" ); document.write( "\n" ); document.write( " The portion in red\r
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\n" ); document.write( "\n" ); document.write( "\"%28sin%28x%29%2Bcos%28x%29%29%5E2+=+highlight%281%29+%2B+2%2Asin%28x%29%2Acos%28x%29\" is equivalent to 1 due to the pythagorean trig identity\r
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\n" ); document.write( "\n" ); document.write( "\"%28sin%28x%29%2Bcos%28x%29%29%5E2+=+1+%2B+2%2Asin%28x%29%2Acos%28x%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"%28sin%28x%29%2Bcos%28x%29%29%5E2+=+1+%2B+2%2Asin%28x%29%2Acos%28x%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"%28sin%28x%29%2Bcos%28x%29%29%5E2+%2B+C+=+1+%2B+2%2Asin%28x%29%2Acos%28x%29+%2B+C\" Add C to both sides\r
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\n" ); document.write( "\n" ); document.write( "We'll let \"C+=+-+3%28cos%28x%29%2Bsin%28x%29%29%2B2\"\r
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\n" ); document.write( "\n" ); document.write( " Plug in \"C+=+-+3%28cos%28x%29%2Bsin%28x%29%29%2B2\"\r
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\n" ); document.write( "\n" ); document.write( " Distribute\r
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\n" ); document.write( "\n" ); document.write( " Combine like terms and do a bit of rearranging.\r
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\n" ); document.write( "\n" ); document.write( "The RHS (right hand side) matches the original expression
\n" ); document.write( "So,\"%28sin%28x%29%2Bcos%28x%29%29%5E2+-+3%28cos%28x%29%2Bsin%28x%29%29%2B2\" is equivalent to \"2%2Asin%28x%29%2Acos%28x%29-3sin%28x%29+-+3cos%28x%29%2B3\" for all real numbers x.\r
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\n" ); document.write( "\n" ); document.write( "Therefore, the final answer is choice A\r
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\n" ); document.write( "\n" ); document.write( "Through graphing technology, we can use programs like GeoGebra to visually verify we have the proper answer.\r
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\n" ); document.write( "\n" ); document.write( "Let
\n" ); document.write( "\"f%28x%29+=+2%2Asin%28x%29%2Acos%28x%29-3sin%28x%29+-+3cos%28x%29%2B3\"
\n" ); document.write( "\"g%28x%29+=+%28sin%28x%29%2Bcos%28x%29%29%5E2+-+3%28cos%28x%29%2Bsin%28x%29%29%2B2\"
\n" ); document.write( "The graph below shows a red and blue striped curve. This is really a solid red curve underneath with a blue dashed curve directly on top of it.
\n" ); document.write( "f(x) = red solid curve, g(x) = blue dashed curve
\n" ); document.write( "The table of values show that f(x) = g(x) for any real x. While this isn't an exhaustive proof by any means, it's a quick way to verify the answer.
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\n" ); document.write( "I recommend you play around with GeoGebra (or any equivalent graphing technology) to turn off/on the second graph to see how it is directly over top the first graph.
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