physics
posted by tingting .
One strategy in a snowball fight is to throw a snowball at a high angle over level ground. While your opponent is watching the first one, a second snowball is thrown at a low angle timed to arrive before or at the same time as the first one. Assume both snowballs are thrown with a speed of 30.0 m/s. The first one is thrown at an angle of 75.0° with respect to the horizontal. how many seconds after the first one is thrown do we throw the second one

It is a curious math problem, which you can prove, that snowballs thrown (45+Theta) will land at the same place.
so if one is 75 deg, the other must be thrown at 15 deg (45+30deg)
Does that help?