Question

Which of the following is a solution to 2sin^(2)x+sinx-1=0

Answer 1

Hello,

$2*sin^2(x)+sin(x)-1=0\\\Delta=1+4*2*1=9=3^2\\sin^2(x)=\frac{-1-3}{4} =-1\ (impossible)\\or\\sin^2(x)=\frac{-1+3}{4} =\dfrac{1}{2}\\sin(x)=\dfrac{\sqrt{2} }{2} \Longrightarrow (x=45^o\ or\ x=135^o)\\or\\sin(x)=-\dfrac{\sqrt{2} }{2} \Longrightarrow (x=315^o\ or\ x=225^o)$

Answer A : 45°