How does cad subtract the intersection of two objects?

Copy two entities, move one side, and then intersect.

Move the reSUlt back, put it away, select the previous two objects, UNI and merge, and then subtract them with su command.

If you don't merge, you have to copy the intersection result and subtract it from the two objects respectively.

Sue:

Subtract one object from another.

Click Modify (m) Entity Edit (n) Difference Set. At the command prompt, enter subtract.

Select the 3D solid, surface or region to subtract. Press enter.

Intersect: Intersect command, directly select two objects and press enter, provided that the position is well placed, and use the move command.

Uni: merge, directly select the object, and press enter.