+14917 2sin^2x-2sinx-1=0
\(2sin^2x-2sinx-1=0\)
\(sinx=z\)
\(2z^2-2z-1=0\)
\(z = {-b \pm \sqrt{b^2-4ac} \over 2a}\)
\(z = {2 \pm \sqrt{2^2+4*2*1} \over 2*2}\)
\(z = {2 \pm \sqrt{12} \over 4}\)
\(z_1=1.3660254 \ Not \ applicable.\ -1 \leq sinx \leq 1\)
\(z_2=-0.3660254\)
\(sinx=z_2=-0.3660254\)
\(x=arcsinx=arcsin-0.3660254\)
\(x=-21°28'15''=-0.3747344\ rad\)
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