Divide and give the..

answer in trigonometric form?
20(cos*(pi/3) + isin*(pi/3)
------------------------------------
4(cos*pi + isin*pi)

The argument (angle) of the quotient of two complex numbers is equal to the difference between the arguments of the numbers.
Therefore:

20(cos*(pi/3) + isin*(pi/3)
------------------------------------ =
4(cos*pi + isin*pi)


5[cos(pi/3-pi)+isin(pi/3-pi)]=

5[cos(-2pi/3)+isin(-2pi/3)]

Though this answer is in the requested form, for some reason there is a tendency to write the answer with a positive angle ("argument")

This can always be done by adding 2pi so the answer can also be written in the form:

5[cos(10pi/3)+isin(10pi/3)]