Both i and -i are sixth roots of -1. There are four others. Find 1 of them and express it in rectangular form

I am very confused with this math problem. Could someone please explain to me how this is done? Thank you!

Z^6= -1= -1+0i
-1+0i = (1,180) in (r,θ) form
= 1cis180

Then z= (-1+0i)^(1/6)
Now, to find roots, raise r^ (1/6) and divide the angle by 6:

= 1^(1/6) cis (180/6)
= 1cis30
= cos30+ isin(30)

= sqr(3)/2 + (1/2)i
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You find the other roots by adding 360 to the angle:

Also z= 1cis (180+360)/6
= cis 90
= cos 90 + isin 90
= i
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Also z= 1cis (180+360+360)/6= cis 150
= cos 150+ isin150
= -sqr(3)/2 +(1/2)i
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Also z= 1cis (210)
= -sqr(3)/2 -(1/2)i
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Also z= 1cis( 270)
= 0+ -1 i
= -i
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There should be six roots, so you can do this 6 times.
Z= 1cis 330
= sqr(3)/2 -(1/2)i

Hoping this helps!