C2.$2.sin(x+\frac{\pi}{4})+sin(x-\frac{\pi}{4})=\frac{3\sqrt{2}}{2}$
$\Leftrightarrow 2[sin(x+\frac{\pi}{4})-\frac{\sqrt{2}}{2}]+[sin(x-\frac{\pi}{4})-\frac{\sqrt{2}}{2}]=0$
$\Leftrightarrow 2[sin(x+\frac{\pi}{4})-sin\frac{\pi}{4}]+[sin(x-\frac{\pi}{4})-\frac{\pi}{4}]=0$
$\Leftrightarrow 4cos(\frac{x}{2}+\frac{\pi}{4})sin\frac{x}{2}+2sin(\frac{x}{2}-\frac{\pi}{4})cos\frac{x}{2}=0$
$\Leftrightarrow -2sin(\frac{x}{2}-\frac{\pi}{4}).sin\frac{x}{2}+sin(\frac{x}{2}-\frac{\pi}{4})cos\frac{x}{2}=0$
$\Leftrightarrow sin(\frac{x}{2}-\frac{\pi}{4})(cos\frac{x}{2}-2sin\frac{x}{2})=0$
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