document.write( "Question 260365: Hello, can you please help me prove that 3cos^2x-2cosx=0? Thank you very much. \n" ); document.write( "

Algebra.Com's Answer #191788 by drk(1908) $\"\"$ $\"About$

You can put this solution on YOUR website!
Hi, think of this as regular factoring steps.
\n" ); document.write( " $\"3%2Acos%5E2%28x%29-2%2Acos%28x%29=0\"$
\n" ); document.write( "step 1 - factor out a cos(x) to get
\n" ); document.write( " $\"cos%28x%29%2A%283cos%28x%29+-+2%29=+0\"$
\n" ); document.write( "step 2 -set each part = 0 and solve for x. We get
\n" ); document.write( "cos(x) = 0
\n" ); document.write( "x = pi/2, or 3pi/2
\n" ); document.write( "3cos(x) -2 = 0
\n" ); document.write( "cos(x) = 2/3
\n" ); document.write( "we estimate this as 48.1 degrees
\n" ); document.write( "--
\n" ); document.write( "so we have 48.1, 90, and 270 degrees
\n" ); document.write( "--
\n" ); document.write( "since this is not an identity, we can't \"prove\" for all x. \n" ); document.write( "

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