I learned this over 20 years ago but it's worth repeating because so many drivers who complain about blind spots are unaware of how to adjust their mirrors so the blind spot is either significantly reduced or disappears all together..
https://www.wikihow.com/Set-Rear‐View-Mirrors-to-Eliminate-Blind-Spots
https://www.caranddriver.com/features/a15131074/how-to-adjust-your-mirrors-to-avoid-blind-spots/
https://www.wikihow.com/Set-Rear‐View-Mirrors-to-Eliminate-Blind-Spots
https://www.caranddriver.com/features/a15131074/how-to-adjust-your-mirrors-to-avoid-blind-spots/