$\cos \theta+\sin \theta=\sqrt{2} \cos \theta$ হলে, $\cos \theta-\sin \theta$ এর মান কত?

$\cos \theta+\sin \theta$ $=\sqrt{2} \cos \theta$ $\Rightarrow \sin \theta$ $=\sqrt{2} \cos \theta-\cos \theta$ $\Rightarrow \sin \theta$ $=(\sqrt{2}-1) \cos \theta$ $\Rightarrow(\sqrt{2}+1) \sin \theta$ $=(\sqrt{2}-1)$ $(\sqrt{2}+1) \cos \theta$ $\Rightarrow \sqrt{2} \sin \theta+\sin \theta$ $=\cos \theta$ $\therefore \cos \theta-\sin \theta$ $=\sqrt{2} \sin \theta$