Scoubidou,

That is correct, think of it this way, it's easier to calculate the area of a rectangle,: width * length.

If you draw out your wings it becomes clearer:



tip + root adds up to one side of the rectangle, 1/2 the total wingspan the other.

The fuse and tail area are normally ignored in the wing area calculation, as they only contribute to directional stability, not lift.
It's a different story with Jets though, for the F-16 for example, the fuselage can generate up to 30% of the total lift amount.

Hope this helps, if not, don't hesitate to ask.
Best Regards,
Gert