How to mill an accurate dimension over sharp corners.

[Parlo]

With parts that are not square it can be difficult to mill & measure exactly when you are at the correct dimension.
The video shows a common triangular shape often used as a strengthening gusset.
For precision it is not advised to try to measure over sharp corners & to ideally measure the part on the machine.
The simple formula gives a size that can be measured the machine & a method to machine the part.