Calculate the area of a triangle given the coordinates of its three vertices.
A (1, 2), B (3, 4), C (5, 6)
The area of the triangle ABC is 5.
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Calculate the area of a triangle given the coordinates of its three vertices.

### Response:
The area of the triangle ABC is 5.