Argument and modules of complex numbers Can you help me to find the argument and modules of this complex number please? 
$$z=\frac{2-i}{-\sqrt {3}-2i}$$

$$z=\frac{2-i}{-\sqrt {3}-2i}\cdot\frac{-\sqrt {3}+2i}{-\sqrt {3}+2i}=\frac{-2\sqrt3+2i-i\sqrt3-2i^2}{3+4}=$$
$$=\frac{2-2\sqrt3+(2-\sqrt3)i}{7}=\frac{2-2\sqrt3}{7}+\frac{2-\sqrt3}{7}i=a+bi$$
then
$$|z|=\sqrt{a^2+b^2}$$
$$\arg z=\arctan\frac{a}{b}$$
