Toán Lớp 11: Giúp e với cần gấp ạ
Cos x – 2 sin^2 x +2=0
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Toán Lớp 11: Giúp e với cần gấp ạ
Cos x – 2 sin^2 x +2=0
Thank
Comments ( 1 )
x = \dfrac{\pi }{2} + k\pi \\
x = \dfrac{{2\pi }}{3} + k2\pi \\
x = – \dfrac{{2\pi }}{3} + k2\pi
\end{array} \right.\)
\cos x – 2{\sin ^2}x + 2 = 0\\
\to \cos x – 2\left( {1 – {{\cos }^2}x} \right) + 2 = 0\\
\to \cos x – 2 + 2{\cos ^2}x + 2 = 0\\
\to 2{\cos ^2}x + \cos x = 0\\
\to \cos x\left( {2\cos x + 1} \right) = 0\\
\to \left[ \begin{array}{l}
\cos x = 0\\
\cos x = – \dfrac{1}{2}
\end{array} \right.\\
\to \left[ \begin{array}{l}
x = \dfrac{\pi }{2} + k\pi \\
x = \dfrac{{2\pi }}{3} + k2\pi \\
x = – \dfrac{{2\pi }}{3} + k2\pi
\end{array} \right.\left( {k \in Z} \right)
\end{array}\)