Toán Lớp 11: Giúp mik với mn : tan2x+tanx=0
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Toán Lớp 11: Giúp mik với mn : tan2x+tanx=0
Comments ( 2 )
x \ne \dfrac{\pi }{4} + \dfrac{{k\pi }}{2}\\
x \ne \dfrac{\pi }{2} + k\pi
\end{array} \right.\)
DK:\left\{ \begin{array}{l}
\cos 2x \ne 0\\
\cos x \ne 0
\end{array} \right. \to \left\{ \begin{array}{l}
x \ne \dfrac{\pi }{4} + \dfrac{{k\pi }}{2}\\
x \ne \dfrac{\pi }{2} + k\pi
\end{array} \right.\\
\tan 2x + \tan x = 0\\
\to \tan 2x = – \tan x\\
\to \tan 2x = \tan \left( { – x} \right)\\
\to 2x = – x + k\pi \\
\to 3x = k\pi \\
\to x = \dfrac{{k\pi }}{3}\left( {k \in Z} \right)
\end{array}\)