Question 839654
{{{sin^2(x)+cos^2(x)=1}}}
{{{(1/3)^2+cos^2(x)=1}}}
{{{cos^2(x)=1-1/9}}}
{{{cos^2(x)=8/9}}}
{{{cos(x)= 0 +- sqrt(8)/3}}}
{{{cos(x)= 0 +- (2/3)sqrt(2)}}}