Why there are two possiles angles for the same range of projectile?

Answer 1

When a projectile is shot at ground level the range formula is this...

d = (v2/g) * sin 2*theta

d=range

v=velocity

g=speed of gravity

sin= sine function

theta=angle that you make when the projectile is shot

In your question you are asking about theta. The maximum distance you will get is when theta is 45 degrees. This is because of gravity. Gravity is pulling down on the object. When something is shot above 45 degrees gravity pull down on the object the same way as it pulls down on the corresponding angle below 45 degrees. When I say corresponding angle look below. Basically the answer to your question is because of gravity.

Corresponding angles...

44 and 46

50 and 40

10 and 80

15 and 75

89 and 1

30 and 60

90 and 0

If you notice they all add up to 90 degrees. 90 degrees is the highest angle that can be shot. If it is greater than 90 degrees then the projectile will go behind you.