By adding yet another edgeloop to make the tri to a quad. Or by merging the vertices together to remove the faceloop that ends in this tri. Or you add an SDS layer, then this tri turns into quads, with a pole.
Another question is if this tri makes trouble at all. When this is a final geometry then you might just be fine with this tri.
you will always have triangles, that is normal. you have to terminate loops somewhere like that sometimes. if you get to animation and find it to be a problem (you most likely wont) then you can just terminate the loop somewhere else.
don't waste time on this, it's a common beginner mistake to read "use quad topology" and then waste tons of time chasing triangles around. It accomplishes nothing because triangles are rarely a problem. if you want to see visual examples of ways to adjust topology check out the wiki, it has plenty of pictures which show different ways.
never try to solve a problem if you cannot demonstrate (repeating something you read is not a demonstration) why it is actually a problem. you'll waste a ton of time doing this.
Sure is all tris under the hood. But for modeling and a clean topology you might want to have quads. Edgeloop tools simply stops at a tri. And sds'ing a tri can lead to a pole, which you might want to avoid. So it can make sense to model away a tri.
Here two solutions to get rid of the tri at this place. But keep in mind that you just move the problem to another location this way. To eliminate the tri you need to redirect the edgeloops. I think you can find quite a few threads about it here. When you search for an example, you already have such a redirected loop in your current mesh. And when you do mirror modeling, and redirect the edgeloop to the mirror plane, then your tri is gone. This all of course only when your tri makes trouble at its current position.
Re-inserting this into the OP's original image ... :
..okay.. if you add: And deleting some loops. .. but yes without further context: making one single triangle into a quad is imposible without adding or deleting some loop and additional re-arangement.. maub like so:
Replies
Another question is if this tri makes trouble at all. When this is a final geometry then you might just be fine with this tri.
Here two solutions to get rid of the tri at this place. But keep in mind that you just move the problem to another location this way. To eliminate the tri you need to redirect the edgeloops. I think you can find quite a few threads about it here. When you search for an example, you already have such a redirected loop in your current mesh. And when you do mirror modeling, and redirect the edgeloop to the mirror plane, then your tri is gone.
This all of course only when your tri makes trouble at its current position.
..okay.. if you add:
And deleting some loops.
but yes without further context: making one single triangle into a quad is imposible without adding or deleting some loop and additional re-arangement.. maub like so: