Question 1086238
{{{sin(3*theta)=cos(3*theta)}}}
and
{{{sin^2(3*theta)+cos^2(3*theta)=1}}}
{{{cos^2(3*theta)+cos^2(3*theta)=1}}}
{{{2cos^2(3*theta)=1}}}
{{{cos^2(3*theta)=1/2}}}
{{{cos(3*theta)=0 +- sqrt(2)/2}}}
So, 
{{{3*theta=45+(360)k}}} and
{{{3*theta=225+(360)k}}}
So then,
{{{theta=15+120k}}}
{{{theta=75+120k}}}
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Theta is 15 not 18 degrees.