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Find the complex cube root of 8.
We have to find the complex cube root of 8.
Answer: The complex cube root of 8 is −1 ± √3i
Let us see how we can find the complex cube root of 8.
Explanation:
We can plot the cube roots of 8 in the complex plane on the circle of radius 2.
So, we can write as,
2(cos(0) + isin(0)) = 2
2(cos(2π/3) + isin(2π/3)) = −1 + √3i = 2ω
2(cos(4π/3) + isin(4π/3)) = −1 − √3i = 2ω2
We will find all of the roots of x3 − 8 = 0 to calculate the complex cube root of 8.
x3 − 8 = (x − 2) (x2 + 2x + 4)
We can solve x2 + 2x + 4 = 0 using the quadratic formula:
x = −b ± √(b2 − 4ac) / (2a)
= −2 ± √22−(4 × 1 × 4)/ 2×1
= −2 ± √−12/2
= −1 ± √3i
Thus, the complex cube root of 8 is given by √8 = −1 ± √3i
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