document.write( "Question 1178808: In this problem, we find all x with 0\n" ); document.write( "\n" ); document.write( "Use sin^2x+cos^2x=1 to find cosx. \n" ); document.write( "
Algebra.Com's Answer #808233 by MathLover1(20849)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "given: \"tan%28x%29+%2Bsec%28x%29+=sqrt%283%29\" and \"0%3C+x+%3C+2pi\"\r
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\n" ); document.write( "\n" ); document.write( "We use the identity: \"sin%5E2%28x%29+%2Bcos%5E2%28+x+%29=+1\" to find \"cos%28x%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%5E2%28+x+%29=+1-sin%5E2%28x%29+\"..........factor\r
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\n" ); document.write( "\n" ); document.write( "\"cos%5E2%28+x+%29=%28+1-sin%28x%29%29%28+1%2Bsin%28x%29%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%5E2%28+x+%29%2F%28+1-sin%28x%29%29=%28+1%2Bsin%28x%29%29\".....1)\r
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\n" ); document.write( "\n" ); document.write( "\"tan%28x%29=sin%28x%29%2Fcos%28x%29\" and \"sec%28x%29=1%2Fcos%28x%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"sin%28x%29%2Fcos%28x%29+%2B1%2Fcos%28x%29+=sqrt%283%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"%28sin%28x%29%2B1%29%2Fcos%28x%29+=sqrt%283%29\".......substitute \"%28+1%2Bsin%28x%29%29\" from 1)\r
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\n" ); document.write( "\n" ); document.write( "\"%28cos%5E2%28+x+%29%2F%28+1-sin%28x%29%29%29%2Fcos%28x%29+=sqrt%283%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%28x%29%2F%281+-+sin%28x%29%29=sqrt%283%29\"\r
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\n" ); document.write( "\n" ); document.write( "use the identity: \"sin%5E2%28x%29+%2Bcos%5E2%28+x+%29=+1\" to find \"sin%28x%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"sin%28x%29=sqrt%281-cos%5E2%28+x+%29%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%28x%29%2F%281+-+sqrt%281-cos%5E2%28+x+%29%29%29=sqrt%283%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%28x%29=%281+-+sqrt%281-cos%5E2%28+x+%29%29%29%2Asqrt%283%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%28x%29%2Fsqrt%283%29=1+-+sqrt%281-cos%5E2%28+x+%29%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%28x%29%2Fsqrt%283%29-1=+-+sqrt%281-cos%5E2%28+x+%29%29\".....square both sides\r
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\n" ); document.write( "\n" ); document.write( "\"%28cos%28x%29%2Fsqrt%283%29-1%29%5E2=+%28-+sqrt%281-cos%5E2%28+x+%29%29%29%5E2\"\r
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\n" ); document.write( "\n" ); document.write( "\"%28cos%28x%29-sqrt%283%29%29%2F%28sqrt%283%29%29%5E2=+1-cos%5E2%28+x+%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"%28cos%28x%29-sqrt%283%29%29%5E2%2F3=+1-cos%5E2%28+x+%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%5E2%28x%29-2cos%28x%29%2Asqrt%283%29%2B3=+3-3cos%5E2%28+x+%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%5E2%28x%29%2B3cos%5E2%28+x+%29-2cos%28x%29%2Asqrt%283%29%2B3-+3=0\"\r
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\n" ); document.write( "\n" ); document.write( "\"4cos%5E2%28+x+%29-2cos%28x%29%2Asqrt%283%29=0\"\r
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\n" ); document.write( "\n" ); document.write( "\"2cos%28x%29%282cos%28+x+%29-sqrt%283%29%29=0\"\r
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\n" ); document.write( "\n" ); document.write( "solutions:\r
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\n" ); document.write( "\n" ); document.write( "if \"2cos%28x%29=0\"=> \"cos%28x%29=0\"\r
\n" ); document.write( "\n" ); document.write( "or\r
\n" ); document.write( "\n" ); document.write( "if \"2cos%28+x+%29-sqrt%283%29=0\"=>\"2cos%28+x+%29=sqrt%283%29\"=>\"cos%28+x+%29=sqrt%283%29%2F2\"\r
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\n" ); document.write( "\n" ); document.write( "Since \"tan+%28x%29\" and \"cos+%28x%29\" are positive, then \"x\" lies in the first quadrant, and in \"sin%28x%29%2Fcos%28x%29+%2B1%2Fcos%28x%29+=sqrt%283%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"cos%28x%29=0\" is denominator, so disregard this solution\r
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\n" ); document.write( "\n" ); document.write( "\"cos+%28x+%29=+sqrt%283%29%2F2\" \r
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\n" ); document.write( "\n" ); document.write( "\"x=+cos%5E-1%28sqrt%283%29%2F2+%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"x=+pi%2F6\" (result in radians)-> your solution\r
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\n" ); document.write( "\n" ); document.write( "convert to degrees\r
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\n" ); document.write( "\n" ); document.write( "\"+x+=+30\"° (degrees)\r
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