Chủ đề này có 3 trả lời

[iamshant]

$cos(\frac{11\pi }{4}-\frac{5x}{2})+sin(\frac{7\pi }{4}-\frac{x}{2})=\sqrt{2}sin(\frac{3x}{2}+\frac{2013\pi }{4})$

[BoFaKe]

$cos(\frac{11\pi }{4}-\frac{5x}{2})+sin(\frac{7\pi }{4}-\frac{x}{2})=\sqrt{2}sin(\frac{3x}{2}+\frac{2013\pi }{4})$

$$cos(\frac{11\pi }{4}-\frac{5x}{2})+sin(\frac{7\pi }{4}-\frac{x}{2})=\sqrt{2}sin(\frac{3x}{2}+\frac{2013\pi }{4}) $$

$$\Leftrightarrow \cos (\frac{\pi }{4}-\frac{5x}{2})+\sin (\frac{\pi}{4}-\frac{x}{2})=\sqrt{2}sin(\frac{3x}{2}+\frac{\pi }{4})$$

$$\Leftrightarrow \sqrt{2}\cos (\frac{\pi }{4}-\frac{5x}{2})+\sqrt{2}\sin (\frac{\pi }{4}-\frac{x}{2})=2sin(\frac{3x}{2}+\frac{\pi }{4})$$

$$\Leftrightarrow \cos \frac{5x}{2}+\sin \frac{5x}{2}+\cos \frac{x}{2}-\sin \frac{x}{2}=2(\sin \frac{3x}{2}+\cos \frac{3x}{2})$$

$$\Leftrightarrow ...$$

 

[darkevil]

$$cos(\frac{11\pi }{4}-\frac{5x}{2})+sin(\frac{7\pi }{4}-\frac{x}{2})=\sqrt{2}sin(\frac{3x}{2}+\frac{2013\pi }{4}) $$

$$\Leftrightarrow \cos (\frac{\pi }{4}-\frac{5x}{2})+\sin (\frac{\pi}{4}-\frac{x}{2})=\sqrt{2}sin(\frac{3x}{2}+\frac{\pi }{4})$$

$$\Leftrightarrow \sqrt{2}\cos (\frac{\pi }{4}-\frac{5x}{2})+\sqrt{2}\sin (\frac{\pi }{4}-\frac{x}{2})=2sin(\frac{3x}{2}+\frac{\pi }{4})$$

$$\Leftrightarrow \cos \frac{5x}{2}+\sin \frac{5x}{2}+\cos \frac{x}{2}-\sin \frac{x}{2}=2(\sin \frac{3x}{2}+\cos \frac{3x}{2})$$

$$\Leftrightarrow ...$$

sai từ dấu tương đương t 1 r

[darkevil]

$cos(\frac{11\pi }{4}-\frac{5x}{2})+sin(\frac{7\pi }{4}-\frac{x}{2})=\sqrt{2}sin(\frac{3x}{2}+\frac{2013\pi }{4})$

đề bạn có sai k

sin (-7.pi/4-x/2) thì ms làm đc