x³ - 3 = 0
x³ = 3
So the zeros are the 3 cube roots of 3
3 = 3[cos(2pn) + i·sin(2pn)]
To get the three cube roots of 3, we use DeMoivre's theorem
using the power of
∛3[cos + i·sin]
To get the first cube root, we let n=0
∛3[cos + i·sin] = ∛3[cos(0) + i·sin(0)] = ∛3[1 + 0i] = ∛3
To get the second cube root of 3, we let n=1
∛3[cos + i·sin] = ∛3[cos + i·sin] = ∛3[ + i·] =
and we can write
So the second cube root of 3 is
To get the third cube root of 3, we let n=2
∛3[cos + i·sin] = ∛3[cos + i·sin]
and since cos = cos, and sin = -sin,
the third cube root is just the conjugate of the
second cube root, or
So the zeros of x³ - 3 are:
∛3, , and
Edwin