cách vẽ bảng biến thiên và đồ thị của hàm số y= 2sin2x trên đoạn (-pi/2;pi/2)

\[\begin{array}{l} y = \sin 2x,\,\,\,x \in \left[ { - \frac{\pi }{2};\,\,\frac{\pi }{2}} \right]\\ \Rightarrow y' = 2\cos 2x = 0\\ \Leftrightarrow \cos 2x = 0 \Leftrightarrow 2x = \frac{\pi }{2} + k\pi \\ \Leftrightarrow x = \frac{\pi }{4} + \frac{{k\pi }}{2}\,\,\left( {k \in Z} \right)\\ x \in \left[ { - \frac{\pi }{2};\,\,\frac{\pi }{2}} \right] \Rightarrow x \in \left\{ { - \frac{\pi }{4};\,\,\frac{\pi }{4}} \right\}\\ Bang\,\,bien\,\,thien:\\ x\,\,\,\,\,\,\,\,\,\,\, - \frac{\pi }{2}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, - \frac{\pi }{4}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{\pi }{4}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{\pi }{2}\\ f'\left( x \right)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, - \,\,\,\,\,\,\,\,\,\,\,\,0\,\,\,\,\,\,\,\,\,\,\,\, + \,\,\,\,\,\,\,\,0\,\,\,\,\,\,\,\,\, - \end{array}\]