Look at this picture, I have to fill the empty vertices.
The shape the face I have to fill is triangle. I can't keep edge loops after adding triangle faces, is there a way to avoid using triangle in this situation and keep edge loops work?
Something like this can split triangle into quads, just cut it with Knife tool K. But geometry will become densier in this place.
P.S. Also, I want to mention that if you are doubting how to subdivide something to quads - use Subsurf Modifier set to Simple mode (Simple - because we need to keep original curvature without smoothing). This is easy and absolutely non-destructive way to see how it can be done. So, add modifier and set viewport shading to wireframe Z and don't forget to enable Draw all edges in object settings.