Toán 11

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noinhobinhyen

$\Leftrightarrow (sin^2x+cos^2x)+(sinx+cosx)+sin2x+cos2x=0$

$sin^2x+cos^2x+sinx+cosx+2sinxcosx+cos^2x-sin^2x=0$

$\Leftrightarrow 2cos^2x+2sinxcosx+sinx+cosx=0$

$\Leftrightarrow (2cosx+1)(sinx+cosx)=0$
 
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