Squeaky Floorboards

I was recommended to come here by r/renovations

My floorboards are getting increasingly squeaky and I was wondering how to fix this?

I have access to underneath (somewhat) easily, so was thinking of tacking a triangular piece of wood in the corner of where the boards meet the beams. It’s just the support beams and then the boards nailed directly to the beams

Would this work? Is there a better way to prevent the squeak?