How to add other faces to an existing UVMap?

Hi guys, i have UV unwrapped the visible part of my mesh and rearranged the UV accordingly to my texture. Now i’ve slightly rotated the main camera in my scene and the new camera angle make some mesh faces visible (they are previously hidden by other faces).
considering i’ve spent a lot in rearranging my existing UV and i do not want to start again with those, there is a way to simply add to my UVMap the new, recently showed up, faces without to recalculate the UVunwrapping for my whole mesh?

Thank you!

Yes, you can select any number of faces and map them, and when you look at the UV-map display, “they will be there somewhere.” (You see this effect in many tutorials, in the sections leading up to “seams” and the various mapping-options that are available, because they want to illustrate the incomprehensible “mash-up” that can so easily occur.) Every face has a corresponding two-dimensional face on the UV map, and it can be anywhere at all.

You might also find, however, that re-mapping the thing really isn’t that hard to do, and, if your camera-moves need to be such that they now “uncover” what you had not previously mapped, you might find that you really have no choice. The human eye can be very discerning, and the slightest “bump” in the texture can be very noticeable.

Thank you sundialsvc4, very precious your advices here and there.

is good simply select some other faces, make UVunwrap and find those somewhere in the existing map. thank you again.