Cube root of unity power

cube roots of unity power

Cube root of unity power 1, 2, 3, 4,5, 6, 7, 8, 9………………..n first we find and proof root power three of unity power 1, 2, 3, and we apply that resultant value to n power of unity.

cube roots of unity power

Suppose that x be a cube root of unity.

Therefore

Cube root of unity power

⇒ x³ = 1

⇒    x³- 1 = 0

⇒  (x – 1)(x²  + x  – 1)  =  0

(i)   x  – 1 = 0

x    =  1

(ii)     x²  + x  – 1  =  0

Applying quadratic formula

Cube root of unity power

Cube root of unity power

thus three cube root of unity are

Cube root of unity power

These root are also called complex cube root

or

imaginary cube root of unity.

Cube root of unity power 2

(A)       Cube root of unity power

After solving this we get

\small \left ( \frac{-1+\sqrt{3\iota }}{2} \right )^{2}       \small =\frac{-1-\sqrt{3\iota }}{2}

(B) Cube root of unity power

After solving we get

Cube root of unity power\small =\frac{-1+\sqrt{3\iota }}{2}

We see that each complex cube root of unity is the square of each other

NOTE

If    \small \omega =\, \frac{-1+\sqrt{3\iota }}{2}       then      \small \small \omega^{2} =\, \frac{-1-\sqrt{3\iota }}{2}

And if

\small \small \small \omega =\, \frac{-1-\sqrt{3\iota }}{2}           then      \small \small \small \omega^{2} =\, \frac{-1+\sqrt{3\iota }}{2}

Sum of cube roots of unity is zero,

that is

1  + ω   +  ω²   =  0    ……………………… A

We know that the cube root of unity

1,    \small \small \small \omega =\, \frac{-1-\sqrt{3\iota }}{2},    \small \small \small \omega^{2} =\, \frac{-1+\sqrt{3\iota }}{2}

putting these value in A

1  +  \small \frac{-1+\sqrt{3\iota }}{2}    +  \small \frac{-1-\sqrt{3\iota }}{2}

solving this we get

0/2  =   0

Hence, cube root of unity = 1 + ω  + ω ²  =0

cube root of unity power 3   that is    ω³    =   1

That is

ω³    =   1× ω    ×   ω²    =(  \small \frac{-1+\sqrt{3\iota }}{2} ) (\small \frac{-1-\sqrt{3\iota }}{2})

ω³    =   1× ω    ×   ω²  =     (-1)²  –  (√ 3 ι) ²    /   4

=    1 – (-3) /4

ω³  =   4 / 4   =1

Therefore, the product of the complex cube  roots of unity  ω³  =   1

Cube roots of unity power 4

we know that    ω³  =   1

Cube roots of unity power 4

Cube root of unity power 15

we know that    ω³  =   1

cube root of unity power 15

Cube roots of unity power 27

we know that    ω³  =   1

\small \small \omega ^{27}=\left ( \omega ^{3} \right )^{9}=\left ( 1 \right )^{9}=1

Cube roots of unity power -1 (negative one)

we know that    ω³  =   1

\small \omega ^{-1}=\omega ^{-3}\times \omega ^{2}=\left ( \omega ^{3} \right )^{-1}\times \omega ^{2}=\omega ^{2}

Cube roots of unity power -12 (negative twelve)

we know that    ω³  =   1

\small \omega ^{-12}=\left ( \omega ^{3} \right )^{-4}=\left ( 1 \right )^{-4}=1

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