Principal root of (-64)^1/6

[Jen123]

Question: Find the Principal root (-64)^1/6. Express the result in the form a + bi.

So far I got:
(-64 + i)
1(cos(1/6)(pi/2) + isin(1/6)(pi/2))
1(cos(pi/12) +isin(pi/12))

Problem: I can't fingure out what to do next pls help thanx

 

[royhaas]

Start with \(\displaystyle 2^6=64\).