You can check if the area of the ABC triangle is 0:

```
[ Ax * (By - Cy) + Bx * (Cy - Ay) + Cx * (Ay - By) ] / 2
```

Of course, you don’t actually need to divide by 2.

You can check if the area of the ABC triangle is 0:

```
[ Ax * (By - Cy) + Bx * (Cy - Ay) + Cx * (Ay - By) ] / 2
```

Of course, you don’t actually need to divide by 2.