Find the angle of elevation of a gun which fire a shell with velocity 120m/s and hit a target on the same level but at 1300m

Answer 1

u = 120 cos T forever
Vi = 120 sin T initially
so
Range = u t = 1300
t = 1300/(120 cos T)

h = 0 + Vi t - 4.9 t^2
0 = Vi t - 4.9 t^2
t = Vi/4.9
so
1300/(120 cos T) = 120 sin T / 4.9

now it is just algebra and trig
remember
cos T sin T = (1/2) sin 2T