[toán 11] lượng giác khó

M

metla2011

[TEX]PT\Leftrightarrow (sin 3x-cosx)^2+(sinx-cosx)^2=0[/TEX]
[TEX]\left{ sin3x=cosx\\sinx=cosx[/TEX]
[TEX]\left{ \left[ x=\frac{\pi}{8}+k\frac{\pi}{2}\\x=\frac{\pi}{4}+k\pi\right. \\x=\frac{\pi}{4}+k\pi[/TEX]
[TEX]\Leftrightarrow x=\frac{\pi}{4}+k\pi[/TEX]
 
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