Cho 

Câu hỏi: Cho $z_1=1+i; z_2=\sqrt{2}-\sqrt{2}i.$ Viết $\frac{z_1}{z_2}$ dưới dạng lượng giác?

A. $\frac{\sqrt{2}}{2}\left(\cos \frac{-\mathrm{\pi }}{2}+i.\sin \frac{-\mathrm{\pi }}{2}\right)$

B. $\frac{\sqrt{2}}{2}\left(\cos \frac{-\mathrm{\pi }}{4}+i.\sin \frac{-\mathrm{\pi }}{4}\right)$

C. $\frac{\sqrt{2}}{2}\left(\cos \frac{\mathrm{\pi }}{4}+i.\sin \frac{\mathrm{\pi }}{4}\right)$

D. $\frac{\sqrt{2}}{2}\left(\cos \frac{\mathrm{\pi }}{2}+i.\sin \frac{\mathrm{\pi }}{2}\right)$