Toán Lớp 11: $y=sin\bigg(\dfrac{9π}{2}-x\bigg)+cosx-1$
Tìm $Miny$ và $Maxy$
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Toán Lớp 11: $y=sin\bigg(\dfrac{9π}{2}-x\bigg)+cosx-1$
Tìm $Miny$ và $Maxy$
Comments ( 2 )
y = \sin \left( {\dfrac{{9\pi }}{2} – x} \right) + \cos x – 1\\
y = \sin \left( {4\pi + \dfrac{\pi }{2} – x} \right) + \cos x – 1\\
y = \sin \left( {\dfrac{\pi }{2} – x} \right) + \cos x – 1\\
y = \cos x + \cos x – 1 = 2\cos x – 1\\
– 1 \le \cos x \le 1\\
\Rightarrow – 2 \le 2\cos x \le 2\\
\Rightarrow – 3 \le y \le 1\\
\Rightarrow \left\{ \begin{array}{l}
\max y = 1 \Rightarrow \cos x = 1 \Rightarrow x = k2\pi \\
\min y = – 3 \Rightarrow \cos x = – 1 \Rightarrow x = \pi + k2\pi
\end{array} \right.\left( {k \in \mathbb Z} \right)
\end{array}$