Algebra.Com's Answer #818371 by ikleyn(52798)![\"\"](\"/images/stars/stars-13.gif\")  
You can put this solution on YOUR website!
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document.write( " I will get the same resulting answer, as Edwin, but will make my analysis differently.\r
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document.write( "To simplify my writing, I will introduce the angle y =  and\r\n" );
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document.write( "will look for angles y such that cos(6y) = cos(y) and 0 <= y <= 90 degrees.\r\n" );
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document.write( "Since cos(6y) = cos(y), it implies one of two possibilities:\r\n" );
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document.write( " (1) EITHER 6y = y + 360n degrees\r\n" );
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document.write( " (2) OR 6y = -y + 360n degrees.\r\n" );
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document.write( "From (1), I have 6y-y = 360n; 5y = 360n; y = 0, 360/5 = 72, (360/5)*2, . . . \r\n" );
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document.write( " Taking into account the restriction on the range, the only possible solutions are 0° and 72°.\r\n" );
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document.write( "From (2), I have 6y+y = 360n; 7y = 360n; y = 0, 360/7 = 51.43 degrees, (360/7)*2, . . .\r\n" );
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document.write( " Taking into account the restriction on the range, the only possible solutions are 0° and 360/7 degrees.\r\n" );
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document.write( "It gives the ANSWER : the only solutions for x are 0 degrees, 2*(360/5) = 144 degrees and 2*(360/7) degrees.\r\n" );
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document.write( "Solved.\r
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