Polar forms of $3i$, $1-i$, $2+i$, $-4$, $2-i\sqrt3$ and $\frac{2-i}{1+4i}$

Write the following complex numbers in polar form:

\[ 3 i , \qquad 1 - i , \qquad 2 + i , \qquad - 4 , \qquad 2 - i { \sqrt { 3 } } , \qquad { \frac { 2 - i } { 1 + 4 i } } , \qquad | 3 + i | . \]