These are for cornices and

crown with a 45 spring angle,

To find the mitre angle

1. The wall angle divided by 2=

2. press tan. (answer will be X )

3. X times 5.5= Y

4. 3.88 divided by Y =

5. press inv. tan.

thats inverse tan (3.88/((tan(angle/2))(5.5)))

To find the bevel angle

1. The wall angle divided by 2=

2. press cos. (answer will be X )

3. X times 3.88= Y

4. Y divided by 5.5=

5. press inv. tan.

thats inverse tan (((cos(angle/2))(3.88 ))/5.5)

There's your two formulae which are a pain in the

butt when on site. They will give the theoretical answer but unless you

build the walls yourself, the angles most likely aren't exactly 90 degrees. So start with those angles and test each corner to find the precise angles that fit that particular corner.