Question 1113683
{{{7 sin^2(x) - 14 sin(x) + 2 = -5}}}
{{{7 sin^2(x) - 14 sin(x) + 7 = 0}}}
{{{7(sin^2(x)- 2 sin(x) + 1)= 0}}}
{{{7(sin(x)-1)^2= 0}}}
{{{(sin(x)-1)^2= 0}}}
{{{sin(x)-1= 0}}}
{{{sin(x)=1}}}
That happens only for {{{pi/2}}} and all co-terminal angles.
So you could say that {{{highlight(x=pi/2+2k*pi)}}} for all {{{k}}} integers.