Question 1082268
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<pre>
{{{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}}} 

is equivalent to 

{{{sin^2(x) - 2*sin(x) + 1}}} = {{{0}}}

{{{(sin(x)-1)^2}}} = {{{0}}}

is equivalent to

sin(x) - 1 = 0  ---->  sin(x) = 1.

The solutions are x = {{{pi/2 + 2k*pi}}},  k = 0, +/-1, +/-2, . . . 
</pre>

Solved.