Posted by **Praphul** on Sunday, December 9, 2012 at 8:23am.

Show that -1/2+ 1/2(i3 root) is a cube root of 1

- math -
**Reiny**, Sunday, December 9, 2012 at 9:53am
Did you mean

show that -1/2 + (1/2)√3 i is a cube root of 1 ??

If so, then show that (-1/2 + (1/2)√3 i )^3 = 1

LS = [ (-1/2) ( 1 - √3i) ]^3

= (-1/2)^3 [ 1 + 3(-√3i) + 3(-√3i)^2 + (-√3i)^3 ]

= (-18) [ 1 - 3√3i + 9i^2 - 3√3 i^3 ]

= (-1/8)(1 - 3√3 - 9 + 3√3i ]

=(-1/8)[-8}

= 1

= RS

Yes, -1/2 + (1/2)√3 i is a cube root of 1

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