https://www.merlinarchery.co.uk/merlin-extras/resource/resource_disciplines/flight_archery.htm
"The angle of the dangle - The optimum angle to shoot at for distance is theoretically 45 . However, as the arrow slows down as it travels due to friction through the air, the flight path is not symmetrical and it is better to shoot at just under 45 . If you are shooting with the wind, aim a degree or so higher; if against it, a degree or so lower."
Flight path is a decaying parabola. Some say 43 degrees is best under no wind conditions.
This too: https://physicstoday.scitation.org/do/10.1063/PT.6.4.20181203a/full/
"Once I know the launch velocity of the arrow, I focus on the optimal launch angle. If the launch velocity is much lower than the terminal velocity, then 45° is best. As the launch velocity increases, the launch angle decreases. For my flight arrow, 41° is the best angle."
So, it gets complicated, eh?