Compound angles

Been struggling with this for a while now.
Having a rectangular block I want to mill a groove whose bottom direction is
inclined to all sides at angles A, B & C (angles measured in the planes of
the sides of the block).
If I am correct the first two steps are:
With the sine vice jaws vertical clamp the block rotated in the vertical
plane of A such that top surface makes angle A with the vice base plane.
Tilt in the vertical plane the sine vice jaws to angle = atan (tanB x cosA)
Now comes the part I can't figure out. I need to set the vice base at some
angle in the X - Y plane (a function of C, A and B) to the X axis of the
mill. What is this function?
Help, corrections much appreciated.

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"Machinist60" fired this volley in news:hvnjc4$1ms$
I believe you need compound miter settings, such as you will find for making depressed picture frames in carpentry.
Compound settings adjust both angles interactively to come up with a "corner angle", and a "slope angle".
For instance, if you wished to cut a frame for 45-degree sloping sides with 90-degree corners, you would NOT merely set the saw for 45-degree tilt and 45-degree angle, or the joint will not match up correctly.
See below, how that angle would actually require to be cut:
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Lloyd E. Sponenburgh
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Don Foreman

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