document.write( "Question 963379: Find the solutions of the equation that are in the interval [0, 2π). (Enter your answers as a comma-separated list. If there is no solution, enter NO SOLUTION.)
\n" ); document.write( "cos 2u − cos u = 0 \n" ); document.write( "
Algebra.Com's Answer #854553 by ikleyn(53875)\"\" \"About 
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\n" ); document.write( "Find the solutions of the equation that are in the interval [0, 2π).
\n" ); document.write( "(Enter your answers as a comma-separated list. If there is no solution, enter NO SOLUTION.)
\n" ); document.write( "cos 2u − cos u = 0
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\n" ); document.write( "\n" ); document.write( "        The solution and the answer in the post by @lwsshak3 both are incorrect.\r
\n" ); document.write( "\n" ); document.write( "        I came to bring a correct solution.\r
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\n" ); document.write( "\n" ); document.write( "cos(2u) − cos u = 0
\n" ); document.write( "cos^2(u) - sin^2(u) - cosu = 0
\n" ); document.write( "cos^2(u) - 1 + cos^2(u) - cosu = 0
\n" ); document.write( "2cos^2(u) - cosu - 1 = 0
\n" ); document.write( "(2cosu+1)(cosu-1)=0
\n" ); document.write( "..
\n" ); document.write( "2cos(u)+1 = 0
\n" ); document.write( "cos(u) = -1/2
\n" ); document.write( "u = 2π/3, 4π/3
\n" ); document.write( "or
\n" ); document.write( "cos(u) - 1 = 0
\n" ); document.write( "cos(u) = 1
\n" ); document.write( "u = 0.\r
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\n" ); document.write( "\n" ); document.write( "Solved correctly.\r
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