Question 1071907
{{{sec(x)=sqrt(2)}}}


{{{1/cos(x)=sqrt(2)}}}


{{{cos(x)=(1/sqrt(2))(sqrt(2)/sqrt(2))=sqrt(2)/2}}}
{{{system(x=pi/4+- 2n*pi,or,7*pi/4+- 2n*pi)}}}, for any integer n.