Question 476462
{{{2(sint)^2-sint=1}}}
Let {{{u=sint}}}, then {{{-1<=u<=1}}}
{{{2u^2-u=1}}}
{{{2u^2-u-1=0}}}
{{{(u-1)(2u+1)=0}}}
{{{u-1=0}}} or {{{2u+1=0}}}
{{{u=1}}} or {{{u=-1/2}}}
{{{sint=1}}} or {{{sint=-1/2}}}
{{{t=pi/2}}} or {{{t=(7*pi)/6}}} or {{{t=(11*pi)/6}}}