Modelação tridimensional EXC 15

Exc 15:
download file at:

http://gaudi.fa.utl.pt/~20108209/15 exc.3dm

open tetraeder model from past excercises:

Command:  _Polygon
Center of inscribed polygon ( NumSides=3 Circumscribed Edge Star Vertical AroundCurve ) _Edge

Command:  Offset
Command:  Offset
Curve offset into one closed curve.
Command:  l
Command:  line
Command:  l
Command:  line
Command:  l
Command:  line
Command:  l
Command:  line
Command:  l
Command:  line

3 curves, 3 surfaces added to selection.
Command:  _Sphere
Creating meshes... Press Esc to cancel

1 surface, 6 curves added to selection.
1 surface, 6 curves added to selection.
4 curves added to selection.
1 surface, 6 curves added to selection.
Command:  Align
Command:  _Undo
Undoing Align
Command:  _Undo
Undoing Sphere
Command:  _Redo
Redoing Sphere
1 surface, 6 curves added to selection.
Command:  mi
Command:  mirror

6 curves, 1 surface added to selection.
Command:  co
Command:  copy
6 curves, 1 surface added to selection.
Command:  M
Command:  _Move
Command:  co
Command:  copy
1 surface, 6 curves added to selection.
Command:  M
Command:  _Move
Command:  _Delete
Command:  Z
Command:  '_Zoom

3 surfaces, 7 curves added to selection.

1 surface added to selection.
1 curve removed from selection.
Command:  Rotate3D
4 surfaces, 7 curves added to selection.
1 curve added to selection.

4 surfaces, 7 curves added to selection.
1 curve removed from selection.
Command:  Rotate3D

2 surfaces, 6 curves added to selection.
Command:  Rotate3D

Command:  _Delete

Command:  _BooleanDifference
3 surfaces added to selection.
10 surfaces added to selection.
Boolean difference in progress... Press Esc to cancel

Creating meshes... Press Esc to cancel
1 surface added to selection.
Command:  _Undo
Undoing Layer - change visibility
Command:  _Undo
Undoing Layer - change visibility
Command:  _Undo
Undoing BooleanDifference
Command:  Rotate3D
Command:  '_CopyToClipboard
Command:  _Undo
Undoing Rotate3D
Command:  '_Paste
3 curves, 4 surfaces added to selection.
Command:  _BooleanDifference
10 surfaces added to selection.
Boolean difference in progress... Press Esc to cancel
Creating meshes... Press Esc to cancel
Command:  _Rotate
Command:  _ViewportProperties
Command:  _Save