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posted by denise on Sunday, July 24, 2011 at 9:01pm.
solve the equation 4cos^2x-1=0
cos^2x = 1/4 cosx = ± 1/2 do you know an angle x , so that cosx = 1/2 ??? and by the CAST rule, isn't that angle in any of the 4 quadrants? hint: cos60° = 1/2
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