Question

Find all solutions to the equation. 7 sin2x - 14 sin x + 2 = -5

Answer 1

There it goes, by the bottom has the answer.

Answer 2

$\bf 7sin^2(x)-14sin(x)+2=-5\implies 7sin^2(x)-14sin(x)+7=0 \\\\\\ \stackrel{\textit{notice, this is just }ax^2+bx+c}{\stackrel{\stackrel{ax^2}{\downarrow }}{sin^2(x)}\stackrel{\stackrel{bx}{\downarrow }}{-2sin(x)}\stackrel{\stackrel{c}{\downarrow }}{+1}}=0\implies [sin(x)-1][sin(x)-1]=0 \\\\\\ sin(x)-1=0\implies sin(x)=1\implies \measuredangle x=sin^{-1}(1)\implies \measuredangle x=\cfrac{\pi }{2} \\\\\\ ~~~~~~~~~~~~~~\stackrel{\textit{and for all solutions using }n \in \mathbb{Z}}{\cfrac{\pi }{2}+2\pi n}$