Question 323911
Solutions are for ({{{0}}},{{{2pi}}})
Two paths to solutions:
{{{cos(4x)=0}}}
{{{4x=pi/2}}} and {{{4x=(3/2)pi}}} 
{{{highlight(x=pi/8)}}} and {{{highlight(x=(3/8)pi)}}} 
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{{{cos(x)-1=0}}}
{{{cos(x)=1}}}
{{{highlight(x=0)}}} and {{{highlight(x=2pi)}}}