Question 853721
{{{sin(theta)=2/5
{{{(cos(theta))^2+(sin(theta))^2=1}}}
{{{(cos(theta))^2+(2/5)^2=1}}}
{{{(cos(theta))^2+(4/25)=25/25}}}
{{{(cos(theta))^2=21/25}}}
{{{cos(theta)=0 +- sqrt(21)/25}}}