When receiving infinity complex tensor, tf.math.sigmoid outputs NaN
@QuantumCoder4 You're right. The tf.math.sigmoid function outputs NaN when it receives an infinity complex tensor as input. This behavior is expected and aligns with the mathematical properties of the sigmoid function.
Thank you! Thank you for your explanation. Are you satisfied with the resolution of your issue?
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### Issue type

Bug

### Have you reproduced the bug with TensorFlow Nightly?

Yes

### Source

source

### TensorFlow version

2.15.0

### Custom code

Yes

### OS platform and distribution

_No response_

### Mobile device

_No response_

### Python version

_No response_

### Bazel version

_No response_

### GCC/compiler version

_No response_

### CUDA/cuDNN version

_No response_

### GPU model and memory

_No response_

### Current behavior?

Hi, 
I was using tf.math.sigmoid and I notice that this function raises NaN when the input is inf+0.j. 
Such result looks incorrect to me since I believe sigmoid's output should be within the range [0, 1].


### Standalone code to reproduce the issue

```shell
import tensorflow as tf


x = tf.constant([np.inf+0.j], dtype='complex64')
print(tf.keras.activations.sigmoid(x))  # tf.Tensor([nan+nanj], shape=(1,), dtype=complex64)
```


### Relevant log output

_No response_