[Term Entry] PyTorch Tensor Operations: .cos()

* Add torch.cos() term entry for PyTorch with syntax and example

* fix: update cos.md to follow Codecademy Docs standards

* Update cos.md

* Update cos.md

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Author: cloecoding

content/pytorch/concepts/tensor-operations/terms/cos/cos.md

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+---
+Title: '.cos()'
+Description: 'Computes the cosine of each element in the input tensor.'
+Subjects:
+  - 'Computer Science'
+  - 'Machine Learning'
+Tags:
+  - 'Deep Learning'
+  - 'PyTorch'
+  - 'Tensors'
+CatalogContent:
+  - 'learn-python-3'
+  - 'paths/machine-learning'
+---
+
+The **`.cos()`** function computes the cosine of each element in the input [tensor](https://www.codecademy.com/resources/docs/pytorch/tensors), applied element-wise, and returns a tensor of the same shape. It's part of PyTorch’s math operations used in scientific computing and deep learning.
+
+## Syntax
+
+```py
+torch.cos(input, *, out=None) → Tensor
+```
+
+**Parameters:**
+
+- `input` (Tensor): Input tensor with elements in radians.
+- `out` (Tensor, optional): Optional tensor to store the output.
+
+**Return value:**
+
+A tensor with the cosine of each element in the input, having the same shape.
+
+## Example 1: Using `.cos()` with a 1D tensor
+
+In this example, `.cos()` computes the cosine of a 1D tensor containing angles in radians:
+
+```py
+import torch
+
+# Create a tensor with values in radians
+x = torch.tensor([0, torch.pi / 2, torch.pi])
+
+# Compute the cosine
+y = torch.cos(x)
+
+print(y)
+```
+
+The output of this code is:
+
+```shell
+tensor([ 1.0000e+00, -4.3711e-08, -1.0000e+00])
+```
+
+## Example 2: Applying `.cos()` with a 2D tensor
+
+In this example, `.cos()` is applied to a 2D tensor of angles in radians:
+
+```py
+import torch
+
+# Create a 2x2 tensor
+matrix = torch.tensor([[0, torch.pi / 3], [torch.pi / 2, torch.pi]])
+
+# Compute the cosine
+result = torch.cos(matrix)
+
+print(result)
+```
+
+The output of this code is:
+
+```shell
+tensor([[ 1.0000e+00,  5.0000e-01],
+        [-4.3711e-08, -1.0000e+00]])
+```