The launching speed of a certain projectile is 9.0 times the speed it has at its maximum height. Calculate the elevation angle at launching.
at start u = u forever
Vi = Vi
u^2 + Vi^2 = 81 u^2
so
Vi^2 = 80 u^2
Vi = 8.94 u
tan A = Vi/u = 8.94
so
A = 83.6 degrees above horizontal