Let z=x+iy, where x,y∈R.
Given ∣z∣=2, so
∣z∣2=x2+y2=2.
Also, ∣z2−i∣=1.
Compute z2:
z2=(x+iy)2=x2−y2+2ixy.
So,
z2−i=(x2−y2)+2ixy−i=(x2−y2)+i(2xy−1).
Therefore,
∣z2−i∣2=(x2−y2)2+(2xy−1)2=1.
Now, we have the system:
\begin{align*}
x^2 + y^2 &= 2 \\
(x^2 - y^2)^2 + (2xy - 1)^2 &= 1
\end{align*}
Let us use polar form: z=reiθ, r=2, so z=2eiθ.
Then z2=2ei2θ, so
z2−i=2ei2θ−i.
Write 2ei2θ=2(cos2θ+isin2θ), so
z2−i=2cos2θ+i(2sin2θ−1).
Therefore,
∣z2−i∣2=(2cos2θ)2+(2sin2θ−1)2=1.
Expand:
\begin{align*}
4\cos^2 2\theta + (4\sin^2 2\theta - 4\sin 2\theta + 1) &= 1 \\
4\cos^2 2\theta + 4\sin^2 2\theta - 4\sin 2\theta + 1 &= 1 \\
4(\cos^2 2\theta + \sin^2 2\theta) - 4\sin 2\theta + 1 &= 1 \\
4(1) - 4\sin 2\theta + 1 &= 1 \\
4 - 4\sin 2\theta + 1 = 1 \\
4 - 4\sin 2\theta = 0 \\
1 - \sin 2\theta = 0 \\
\sin 2\theta = 1
\end{align*}
So 2θ=2π+2πk, k∈Z.
Thus θ=4π+πk.
Therefore, the solutions are
z=2ei(4π+πk)
for k∈Z.
Explicitly, for k=0:
z1=2ei4π=2(cos4π+isin4π)=2(22+i22)=1+i.
For k=1:
z2=2ei(45π)=2(cos45π+isin45π)=2(−22−i22)=−1−i.
Thus, the solutions are z=1+i and z=−1−i.