Refer to the diagram below.
This discussion operates under a basic analysis that overlooks air resistance and variations in the terrain the missile traverses.
Let V₀ be the launch velocity, at an angle θ to the horizontal.
The horizontal velocity component equals V₀ cosθ.
If the flight duration is

, then

where r represents the missile's range.
The time t at which the missile is at ground level is expressed by

where g signifies acceleration due to gravity.
t = 0 signifies the missile's launch. Thus

Consequently,

Typically, an angle of θ=45° is optimal for achieving maximum range, resulting in

This discussion applies more accurately to a scud missile than to a powered, guided missile.
Response:

Usually, θ=45°