f(z)=∣z∣2=zzˉ
If f is differentiable at z=z0
Then ∂zˉ∂f∣z=zˉ=0
Now
∂zˉ∂f=zfor z(=0)∈⊈∂zˉ∂f=0⟹f(z)=∣z∣2 is not differential at z(=)=0∈⊈
To check at z=0
f′(0)=z→0limz−0f(z)−f(0)f′(0)=z→0limzzzˉ−0f′(0)=0
Hence f(z) is differentiable at z=0 only.
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