[Toán 11]lg

L

lovelycat_handoi95

Đk : [TEX] cos3x \not=0 [/TEX]

[TEX]\Leftrightarrow sin^23x-\sqrt{3}sin3x+\frac{3}{4}+tan^23x-2\sqrt{3}sin3x+3=0\\ \Leftrightarrow (sin3x-\frac{\sqrt{3}}{2})^2+(tan3x-\sqrt{3})^2=0 \\ \Leftrightarrow \left{sin3x-\frac{\sqrt{3}}{2}=0\\tan3x-\sqrt{3}=0 [/TEX]

[TEX]\Leftrightarrow x= \frac{\pi}{9}+k\frac{2\pi}{3} ; k \in Z[/TEX]
 
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